View source for Patapsco River

{{short description|River in Maryland, United States}}
{{Use American English|date=February 2025}}
{{Use dmy dates|date=March 2024}}
{{Infobox river
| name                = Patapsco River
| native_name         = {{native name|alg|Potapskut}}
| name_other          = The River of History
| name_etymology      = 
| image               = Patapsco fg01.jpg
| image_caption       = [[Patapsco Valley State Park]] at [[Catonsville, Maryland|Catonsville]]
| map                 = Patapscomap (cropped).png
| map_size            = 250
| map_caption         = Patapsco River Watershed
| pushpin_map         = 
| pushpin_map_size    = 250
| pushpin_map_caption = 
| subdivision_type1   = Country
| subdivision_name1   = United States
| subdivision_type2   = State
| subdivision_name2   = [[Maryland]]
| subdivision_type3   = Region
| subdivision_name3   = [[Baltimore metropolitan area]], [[Patapsco Valley]]
| subdivision_type4   = 
| subdivision_name4   = 
| subdivision_type5   = Cities
| subdivision_name5   = [[Baltimore]], [[Elkridge, Maryland|Elkridge]], [[Ellicott City, Maryland|Ellicott City]]
| length              = 63 km
| width_min           = 
| width_avg           = 
| width_max           = 
| depth_min           = 
| depth_avg           = 
| depth_max           = 
| discharge1_location= 
| discharge1_min      = 
| discharge1_avg      = 
| discharge1_max      = 
| source1             = 
| source1_location    = [[Parr's Spring]]
| source1_coordinates = {{coord|39|21|16|N|77|10|4|W|display=inline}}
| source1_elevation   = {{cvt|260|ft}}
| mouth               = [[Chesapeake Bay]]
| mouth_location      = [[Baltimore]]
| mouth_coordinates   = {{coord|39|10|48|N|76|26|24|W|display=inline,title}}
| mouth_elevation     = {{cvt|0|ft}}
| progression         = 
| river_system        = 
| basin_size          = {{cvt|950|sqmi|km2|-1}}
| tributaries_left    = [[North Branch (Patapsco River tributary)|North Branch]]
| tributaries_right   = [[South Branch (Patapsco River tributary)|South Branch]]
}}
[[File:Inner Harbor from the Baltimore Aquarium.jpg|thumb|right|300px|The [[Inner Harbor]] viewed from the [[Baltimore Aquarium]]]]
[[File:Liberty Reservoir Aerial.jpg|thumb|right|300px|Liberty Reservoir]]
[[File:Herbert Run cleanup.jpg|thumb|right|Volunteers at a community cleanup of Herbert Run, a tributary of the Patapsco River running through [[Arbutus, Maryland]]]]

The '''Patapsco River''' ({{IPAc-en|p|ə|ˈ|t|æ|p|ˌ|s|k|oʊ}} {{respell|pə|TAP|skoh}} {{Audio|En-patapsco.ogg| |help=no}}) mainstem is a {{convert|39|mi|km|adj=mid}}<ref name="NHD">{{Cite web |title=The National Map - Advanced Viewer |url=https://apps.nationalmap.gov/viewer/ |access-date=5 April 2023 |website=apps.nationalmap.gov |archive-date=2 February 2021 |archive-url=https://web.archive.org/web/20210202060756/https://apps.nationalmap.gov/viewer/ |url-status=live }}</ref> [[river]] in central [[Maryland]] that flows into [[Chesapeake Bay]]. The river's tidal portion forms the harbor for the city of [[Baltimore]]. With its South Branch, the Patapsco forms the northern border of [[Howard County, Maryland]]. The name "Patapsco" is derived from the [[Eastern Algonquian languages|Algonquian]] ''pota-psk-ut'', which translates to "backwater" or "tide covered with froth".<ref>{{cite web |url=http://www.bayjournal.com/article/ghosts_of_industrial_heyday_still_haunt_baltimores_harbor_creeks |title=Ghosts of industrial heyday still haunt Baltimore's harbor, creeks |publisher=Chesapeake Bay Journal |access-date=8 September 2012 |archive-date=1 October 2018 |archive-url=https://web.archive.org/web/20181001165128/https://www.bayjournal.com/article/ghosts_of_industrial_heyday_still_haunt_baltimores_harbor_creeks |url-status=dead }}</ref>

==History==
[[John Smith of Jamestown|Captain John Smith]] was the first European to explore the river, noting it on his 1612 map as the Bolus River. The "Red river", named after the clay color, is considered the "old Bolus", as other branches were also labeled Bolus on maps.<ref>{{cite book |title=The Chronicles of Baltimore: Being a Complete History of Baltimore Town |author=John Thomas Scharf |page=8 }}</ref> As the river was not navigable beyond Elkridge, it was not a significant path of commerce; in 1723, only one ship was listed as serving the northern branch, and four others operating around the mouth.<ref>{{cite book |title=The Chronicles of Baltimore: Being a Complete History of Baltimore Town |author=John Thomas Scharf |page=18 }}</ref>

The first land record regarding Parr's Springs, the source of the South Branch, dates from 1744, when John Parr laid out a {{convert|200|acre|ha}} tract he called Parr's Range. During the Civil War, Parr's Spring was a stop for the [[Army of the Potomac]]'s [[David McMurtrie Gregg|Brig. Gen. David M. Gregg]]'s cavalry, on 29 June 1863, while en route to [[Gettysburg, Pennsylvania]].<ref>{{cite book |author=Frederic Shriver Klein |title=Just South of Gettysburg: Carroll County, Maryland in the Civil War: Personal Accounts and Descriptions of a Maryland Border County |publisher=Historical Society of Carroll County |year=2000 |page=247 }}</ref> Parr's Spring was dug to form a {{convert|1.75|acre|m2}} pond in the 1950s, filled by seven spring heads that form the headwaters of the South Branch of the Patapsco River.<ref>{{cite news |author=Sheridan Lyons |date=15 May 2000 |title=Beneath the pier, 4 counties meet |url=https://www.baltimoresun.com/2000/05/15/beneath-the-pier-4-counties-meet-history-the-waters-of-parrs-spring-near-mount-airy-flow-over-a-unique-convergence/ |access-date=16 September 2018 |newspaper=The Baltimore Sun }}</ref>

Beginning in the 1770s, the Patapsco River became the center of Maryland industrialization.<ref name=Travers>{{cite book |title=The Patapsco: Baltimore's River of History |author=Paul J. Travers |publisher=Schiffer Publishing Limited |year=2016 |isbn=978-0-87033-644-7 |page=220 |url=https://books.google.com/books?id=-b8lAAAAMAAJ&q=patapsco%20%22river%20of%20history%22 |access-date=14 September 2018 }}</ref> Milling and manufacturing operations abounded along the river throughout the eighteenth and nineteenth centuries, generally powered by small dams. The [[Baltimore and Ohio Railroad]]'s [[Old Main Line Subdivision|original main line]] was constructed in 1829 west along the Patapsco Valley; the nation's first railroad, the route remains, though much altered. Many railroad bridges were built in the valley, including the [[Thomas Viaduct]], which is still in use, and the [[Patterson Viaduct]], now in ruins. The 1907 [[Bloede dam|hydropower]] Bloede's Dam powered flour mills.

An 1868 flood washed away 14 houses and killed 39 people around [[Ellicott City]]. A 1923 flood topped bridges. In 1952, an {{cvt|8|ft}} wall of water swept the shops of Ellicott City. A 1956 flood severely damaged the [[Thistle Manufacturing Company|Bartigis Brothers plant]].<ref>{{cite news |newspaper=The Times (Ellicott City) |date=31 March 1965 |title=The Patapsco River Creator-Destroyer }}</ref> In 1972, rainfall from the remnants of [[Hurricane Agnes]] damaged Ellicott City and the Old Main Line. Two died in the July [[2016 Maryland flood]] that ravaged Main Street in Ellicott City, followed two years later by a May [[2018 Maryland flood]] that took the life of a rescuer.<ref>{{Cite web |url=https://www.11alive.com/amp/article?section=weather&headline=devastating-dangerous-ellicott-citys-main-street-hit-with-flooding-again&contentId=65-558994116 |title='Devastating, dangerous' &#124; Ellicott City's Main Street hit with flooding again |website=www.11alive.com |date= |access-date= }}</ref>

The mouth of the Patapsco River forms Baltimore Harbor, the site of the [[Battle of Baltimore]] during the [[War of 1812]]. This is where [[Francis Scott Key]], aboard the British {{HMS|Tonnant|1798|6}}, wrote "[[The Star-Spangled Banner]]", a poem later set to music as the national anthem of the United States. Today, a red, white, and blue buoy marks where the ship was anchored.

[[Bloede's Dam]], a hydroelectric dam built in 1906, was on the Patapsco River within [[Patapsco Valley State Park]], a nearly complete barrier to [[anadromous]] fish passage. Although a fish ladder was installed in 1992, it blocked five of six native fish species trying to run upstream to spawn.<ref name="Bloede">{{cite report |url=http://dnr.maryland.gov/streams/Publications/2012_PatapscoFinalReport.pdf |title=Patapsco River Dam Removal Study: Assessing Changes in American Eel Distribution and Aquatic Communities – Final Report |author=William Harbold |author2=Scott Stranko |date=1 May 2013 |publisher=Maryland Department of Natural Resources |author3=Jay Kilian |author4=Matt Ashton |author5=Patrick Graves |access-date=4 September 2018 }}</ref> Efforts to remove Bloede's Dam began in the 1980s when nine drowning deaths occurred, and also to restore fish passage to a large portion of the Patapsco River watershed.<ref>{{cite news |author=Rachael Pacella |date=23 March 2016 |title=Bids set to go out for removal of Bloede Dam at Patapsco Valley State Park |newspaper=The Baltimore Sun }}</ref><ref>{{cite news |date=22 May 1982 |title=Man, 18, drowns near dam |newspaper=The Baltimore Sun |page=C2 }}</ref> Dam demolition began on 12 September 2018, opening the fishery and creating a rocky rapid for kayaking.<ref>{{Cite web |date= |title=Bloede Dam |url=http://dnr.maryland.gov/fisheries/pages/fishpassage/bloede.aspx |access-date=29 March 2024 |website=dnr.maryland.gov }}</ref> Two dams upstream of Bloede's Dam, Simkins and Union, were removed in 2010.<ref>{{Cite news |author=Scott Dance |date=5 September 2018 |title=After a century on the Patapsco River, Bloede Dam's removal set to begin with a blast |url=http://www.baltimoresun.com/news/maryland/environment/bs-md-co-bloede-dam-removal-20180905-story.html |access-date=5 September 2018 |newspaper=The Baltimore Sun |archive-date=5 September 2018 |archive-url=https://web.archive.org/web/20180905225339/http://www.baltimoresun.com/news/maryland/environment/bs-md-co-bloede-dam-removal-20180905-story.html |url-status=dead }}</ref><ref name="Cui">{{cite journal |author=Yantao Cui |author2=Mathias J. Collins |author3=Mary Andrews |author4=Graham C. Boardman |author5=John K. Wooster |author6=Marty Melchior |author7=Serena McClain |year=2018 |title=Comparing 1-D sediment transport modeling with field observations: Simkins Dam removal case study |journal=International Journal of River Basin Management |volume=17 |issue=2 |pages=1–13 |doi=10.1080/15715124.2018.1508024 |s2cid=133928458 }}</ref> The removal of Bloede's Dam leaves Daniels Dam, {{convert|9|mi|km}} upstream, as the last remaining dam along the mainstem Patapsco River.<ref name="Bloede" />

In the early hours of 26 March 2024, the {{convert|1.6|mile|km|-long|adj=mid}} [[Francis Scott Key Bridge (Baltimore)|Francis Scott Key Bridge]], which carried [[Interstate 695 (Maryland)|Interstate 695]] over the Patapsco River, was struck by a [[container ship]] and [[Francis Scott Key Bridge collapse|partially collapsed]] into the river.<ref>{{Cite web |date=26 March 2024 |title=Baltimore bridge collapses after powerless cargo ship rams into support column; 6 presumed dead |url=https://apnews.com/article/baltimore-bridge-collapse-53169b379820032f832de4016c655d1b |access-date=26 March 2024 |website=AP News |language=en |archive-date=26 March 2024 |archive-url=https://web.archive.org/web/20240326110240/https://apnews.com/article/baltimore-bridge-collapse-53169b379820032f832de4016c655d1b |url-status=live }}</ref>

==Course==
The {{convert|19.4|mi|km|adj=mid|-long}}<ref name="NHD" /> South Branch rises at Parr's Spring, where [[Howard County, Maryland|Howard County]], [[Carroll County, Maryland|Carroll]], [[Frederick County, Maryland|Frederick]], and [[Montgomery County, Maryland|Montgomery]] counties meet. The latter begins at elevation {{convert|780|ft|m}} on [[Parr's Ridge]], just south of Interstate 70 and east of Ridge Road ([[Maryland State Route 27|Highway 27]]), {{convert|2|mi|0}} south of [[Mount Airy, Maryland]].<ref name="NHD" /> The South Branch Patapsco River traces the southern boundary of [[Carroll County, Maryland|Carroll County]] and the northern boundary of [[Howard County, Maryland|Howard County]].

The North Branch flows {{convert|20.9|mi}}<ref name="NHD" /> southward from its origins in Carroll County. [[Liberty Reservoir|Liberty Dam]] and its reservoir on the North Branch are major components of the Baltimore City water system.<ref>Baltimore County Department of Environmental Protection and Resource Management. Towson, MD. [http://www.baltimorecountymd.gov/Agencies/environment/watersheds/ep_patapmain.html "Patapsco River Watershed."] 13 July 2009.</ref>

The Patapsco River mainstem begins at the [[confluence]] of the North and South Branches, near [[Marriottsville, Maryland|Marriottsville]], about {{convert|15|mi}} west of downtown Baltimore. Through most of its length, the Patapsco is a minor river flowing mostly through a narrow valley.  [[Patapsco Valley State Park]] extends along {{convert|32|mi|km|0}} of the Patapsco and its branches, encompassing {{convert|14000|acre}} in five areas. The river cuts a gorge 100 to 200 feet (35–70 m) deep within the park, with rocky cliffs and tributary waterfalls.

The last {{convert|10|mi|km|0}}, form a large tidal [[estuary]] inlet of [[Chesapeake Bay]]. Two lobes of the harbor deviate from the "mainstem" harbor: the Middle Branch Patapsco River, into which the [[Gwynns Falls]] flows; and the Northwest Branch Patapsco River, into which the [[Jones Falls]] flows. The inner part of this estuary provides the [[harbor]] of [[Baltimore]]. [[Thoms Cove]] is further down the main harbor. The Patapsco estuary is south of the [[Back River (Maryland)|Back River]] and north of the [[Magothy River]].

== Tributaries ==
The Patapsco has a [[drainage basin|watershed]] (including the water surface) of {{convert|950|sqmi|km2|-1}}.<ref name="Cui" /> {{div col|colwidth=30em}}
* Deep Run (Carroll County)
* Board Run (Baltimore County)
* Roaring Run (Carroll County)
* [[Liberty Reservoir]] (Carroll/Baltimore Counties)
* Piney Run (Carroll County)
* Keysers Run (Baltimore County)
* Beaver Run (Carroll County)
* Norris Run (Baltimore County)
* Timber Run (Baltimore County)
* Middle Run (Carroll County)
* Morgan Run (Carroll County)
* Locust Run (Baltimore County)
* Snowdens Run (Carroll County)
* Falls Run (Baltimore County)
* South Branch Patapsco River
* Davis Branch (Howard County)
* Brice Run (Baltimore County)
* Bens Run (Baltimore County)
* Cedar Branch (Baltimore County)
* Miller Run (Baltimore County)
* Sucker Branch (Howard County)
* Tiber River (Howard County)
* Cooper Branch (Baltimore County)
* Bonnie Branch (Howard County)
* Sawmill Branch (Baltimore County)
* Cascade Falls (Howard County)
* Soapstone Branch (Baltimore County)
* Rockburn Branch (Howard County)
* [[Deep Run (Patapsco River)|Deep Run]] (Howard/Anne Arundel County)
* Stony Run (Anne Arundel County)
* [[Herbert Run]] (Baltimore County)
* Holly Creek (Anne Arundel County)
* Middle Branch to [[Gwynns Falls]] (Baltimore City)
* [[Inner Harbor|Northwest Harbor]] to [[Jones Falls]] (Baltimore City)
* Colgate Creek (Baltimore City)
* [[Curtis Creek]] (Baltimore City)
* Bear Creek (Baltimore County)
* Cox Creek (Anne Arundel County)
* Stoney Creek (Anne Arundel County)
* Rock Creek (Anne Arundel County)
* Old Road Bay (Baltimore County)
* Bodkin Creek (Anne Arundel County)
{{div col end}}

==Ecology and conservation==
The removal of Bloede's Dam in September 2018, opened up {{convert|65|mi|km}} of the Patapsco River watershed, which will potentially restore spawning runs of at least six species of native [[anadromous]] fish: [[alewife (fish)|alewife]] (''Alosa pseudoharengus''), [[blueback herring]] (''Alosa aestivalis''), [[American shad]] (''Alosa sapidissima''), [[hickory shad]] (''Alosa mediocris''), [[striped bass]] (''Morone saxatilis''), [[sea lamprey]] (''Petromyzon marinus''), as only one species, sea lamprey, were found using the Bloede's Dam fish ladder in 2012.<ref name=Bloede/> One [[catadromous]] species would likely also benefit, the [[American eel]] (''Anguilla rostrata''), a fish species that lives in freshwater and migrates to the ocean to breed. The Bloede's Dam removal project was led by American Rivers and the [[Maryland Department of Natural Resources]].<ref name=Bloede/>

Now that Bloede's Dam has been removed, removal of Daniels Dam upstream on the mainstem Patapsco River would open to anadromous fishes the remaining {{convert|6.5|mi|km}} of Patapsco River mainstem, the entire {{convert|19.4|mi|km}} length of the South Branch Patapsco River, {{convert|3.5|mi|km}} of the North Branch Patapsco River up to the [[Liberty Reservoir|Liberty Dam]], and many of these rivers' tributaries.<ref name=NHD/>

==Water quality==
The eastern portion of the Patapsco River is in a highly urbanized area and is subject to extensive stormwater [[urban runoff|runoff]] and other forms of [[water pollution]]. The [[Maryland Department of the Environment]] has identified the Lower North Branch as containing high levels of [[Heavy metal (chemistry)|heavy metals]] ([[chromium]], [[arsenic]], [[cadmium]], [[copper]], [[mercury (element)|mercury]], [[nickel]], [[lead]], [[selenium]], and [[zinc]]), as well as [[phosphorus]], [[fecal coliform bacteria]], and [[PCBs]].<ref>
{{cite web |title=TMDLs and Water Quality Plans for the Lower North Branch Patapsco River |url=https://mde.maryland.gov/programs/water/TMDL/Pages/Patapsco-River-LNB.aspx |access-date=12 March 2022 |publisher=Maryland Department of the Environment (MDE) |location=Baltimore, MD }}</ref> The [[Piney Run Park#Piney Run Reservoir|Piney Run Reservoir]] on the South Branch of the Patapsco is polluted by excess levels of phosphorus and sediment.<ref>{{cite web |title=TMDLs and Water Quality Plans for the South Branch Patapsco River |url=https://mde.maryland.gov/programs/water/TMDL/Pages/Patapsco-River-SB.aspx |access-date=12 March 2022 |publisher=MDE }}</ref>

Environmental nonprofit organizations, such as The Friends of Patapsco Valley & Heritage Greenway, Inc. (PHG), lead clean-up efforts by the residents of surrounding communities. From 2006 to 2012, PHG volunteers participated in 183 stream clean-ups, removing 264 tons of trash from the streams of the Patapsco Valley watershed.<ref>{{cite web |url=http://www.patapscoheritagegreenway.org/ |title=Protecting the Valley |publisher=Friends of Patapsco Valley & Heritage Greenway, Inc. |access-date=24 May 2012 }}</ref>

== Recreation ==
Recreational swimming is possible in areas of the Patapsco River, sometimes involving rope swings, inner tubing, and wading. The river also serves as a venue for rafting.
The Patapsco is also great for fishing. The MD DNR stocks parts of Patapsco State Park in the early spring and offers some pretty decent trout fishing. The Northern Snakehead has also made the Patapsco their home. They can be found from historic Ellicott City to the harbor.

==Crossings==
This is a list of all crossings of the main stem of the Patapsco River, as well as its two downstream short branches, the Middle Branch and Northwest Branch. Listings start downstream and continue upstream to the sources of the rivers.
{| class=wikitable
!Image
! Crossing
! Carries
! Location
!Opened
!Notes
|-
! colspan="6" |Anne Arundel County – Baltimore County
|- style="background-color: #d3d3d2;"
|[[File:The Francis Scott Key Bridge (Baltimore).jpg|200x200px|alt=]]
|[[Francis Scott Key Bridge (Baltimore)|Francis Scott Key Bridge]]
|{{jct|state=MD|I|695|name1=}}
|[[Baltimore]]
|1977–2024
|[[Francis Scott Key Bridge collapse|Collapsed after being struck by a container ship on 26 March 2024]]
|-
|[[File:2016-08-12 15 49 22 View north along Interstate 895 (Baltimore Harbor Tunnel) in Baltimore City, Maryland.jpg|200x200px|alt=]]
|[[Baltimore Harbor Tunnel]]
|{{jct|state=MD|I|895|name1=}}
|[[Baltimore]]
|1957
|$4.00 toll
|-
|[[File:Fort McHenry Tunnel Bore 2.jpg|200x200px|alt=]]
|[[Fort McHenry Tunnel]]
|{{jct|state=MD|I|95}}
|[[Baltimore]]
|1985
|Crosses Northwest Branch only; $4.00 toll
|-
| rowspan="4" |[[File:I-395-Downtown Baltimore.JPG|alt=|200x200px]]
|Hanover Bridge
|{{jct|state=MD|MD|2|name1=}}
|[[Baltimore]]
|
|Crosses Middle Branch only
|-
|Spring Garden Swing Bridge
|[[Western Maryland Railway]]
|[[Baltimore]]
|1904<ref>{{Cite web |title=Spring Garden Swing Bridge |url=https://baltimoreblueway.org/sightseeing-landmarks/spring-garden-swing-bridge |access-date=12 September 2024 |website=Baltimore Blueway |language=en-US }}</ref>
|Crosses Middle Branch only
|-
|Ridgleys Cove interchange
|{{jct|state=MD|I|95|name1=}}
{{jct|state=MD|I|395|name1=}}
|[[Baltimore]]
|
|Crosses Middle Branch only
|-
|Light rail bridge
|[[Baltimore Light RailLink]]
|[[Baltimore]]
|
|Crosses Middle Branch only
|-
|
|Hanover and Potee Street Bridges
|{{jct|state=MD|MD|2|name1=}}
|[[Baltimore]]
|1973
|Hanover Street Bridge reconstructed in 2005<ref>{{cite web |url=https://www.google.co.uk/maps/place/39.246423,+-76.612265 |title=Potee Street Bridge |website=www.google.com |date= |access-date=29 March 2024 }}</ref>
|-
|
|Curtis Bay Branch Railroad bridge
|[[Baltimore and Ohio Railroad|B&O]] [[Baltimore Terminal Subdivision|Curtis Bay Branch]]
|[[Baltimore]]
|
|
|-
|
|Patapsco Avenue bridge
|Patapsco Avenue
|[[Brooklyn, Baltimore]]
|1961
|
|-
|
|I-895 bridge near South West Area Park
|{{jct|state=MD|I|895|name1=}}
|[[Baltimore Highlands, Maryland|Baltimore Highlands]]
|1958
|Refurbished in 2019<ref>{{cite web |url=https://www.google.com/maps/@39.2291029,-76.6337158,3a,17.4y,245.96h,64.53t/data=!3m6!1e1!3m4!1s6Mo7bXPmgUFflBsB0d0niw!2e0!7i16384!8i8192 |title=I-895 bridge |website=www.google.com |date= |access-date=29 March 2024 |archive-date=5 April 2023 |archive-url=https://web.archive.org/web/20230405043705/https://www.google.com/maps/@39.2291029,-76.6337158,3a,17.4y,245.96h,64.53t/data=!3m6!1e1!3m4!1s6Mo7bXPmgUFflBsB0d0niw!2e0!7i16384!8i8192 |url-status=live }}</ref>
|-
|
|Central Light Rail bridge
|[[Baltimore Light Rail]]
|[[Baltimore Highlands, Maryland|Baltimore Highlands]]
|1908
|Previously used for the [[Baltimore and Annapolis Railroad]]
|-
|
|Old Annapolis Road bridge
|{{jct|state=MD|MD|648|name1=}}
|[[Baltimore Highlands, Maryland|Baltimore Highlands]]
|
|
|-
|
|BW Parkway bridge
|{{jct|state=MD|MD|295|name1=}}
|[[Baltimore Highlands, Maryland|Baltimore Highlands]]
|1948
|Refurbished in 1985<ref>{{cite web |url=https://www.google.com/maps/@39.2288565,-76.6501202,3a,39.8y,114.96h,55.7t/data=!3m6!1e1!3m4!1sq_Or4af5CwQXKtz-UIIeWg!2e0!7i16384!8i8192 |title=BW Parkway bridge, MD 295 |website=www.google.com |date= |access-date=29 March 2024 |archive-date=5 April 2023 |archive-url=https://web.archive.org/web/20230405045206/https://www.google.com/maps/@39.2288565,-76.6501202,3a,39.8y,114.96h,55.7t/data=!3m6!1e1!3m4!1sq_Or4af5CwQXKtz-UIIeWg!2e0!7i16384!8i8192 |url-status=live }}</ref>
|-
|
|Hammonds Ferry Road bridge
|Hammonds Ferry Road
|[[Linthicum, Maryland|Linthicum]]<br />[[Lansdowne, Maryland|Lansdowne]]
|1961
|
|-
|
|Baltimore Beltway bridge
|{{jct|state=MD|I|695|name1=}}
|[[Linthicum, Maryland|Linthicum]]<br />[[Lansdowne, Maryland|Lansdowne]]
|1958
|Refurbished in 1982<ref>{{cite web |url=https://www.google.com/maps/@39.2288743,-76.6643918,3a,16.5y,75.37h,73.69t/data=!3m6!1e1!3m4!1sogHFpOyuPRLoMf6EdczAaA!2e0!7i16384!8i8192 |title=Baltimore Beltway bridge |website=www.google.com |date= |access-date=29 March 2024 |archive-date=5 April 2023 |archive-url=https://web.archive.org/web/20230405043704/https://www.google.com/maps/@39.2288743,-76.6643918,3a,16.5y,75.37h,73.69t/data=!3m6!1e1!3m4!1sogHFpOyuPRLoMf6EdczAaA!2e0!7i16384!8i8192 |url-status=live }}</ref>
|-
|
|Northeast Corridor bridge
|[[Amtrak]] [[Northeast Corridor]]
|[[Linthicum, Maryland|Linthicum]]<br />[[Halethorpe, Maryland|Halethorpe]]
|
|
|-
|
|I-195 bridge
|{{jct|state=MD|I|195|name1=}}
|[[Elkridge, Maryland|Elkridge]]<br />[[Halethorpe, Maryland|Halethorpe]]
|1988
|
|-
! colspan="6" |Howard County – Baltimore County
|-
|
|I-895 bridge
|{{jct|state=MD|I|895|name1=}}
|[[Elkridge, Maryland|Elkridge]]<br />[[Relay, Maryland|Relay]]
|1973
|On/off ramp bridges flank US 1 bridge to north and south
|-
|
|Patapsco River Bridge
|{{jct|state=MD|US|1|name1=}}
|[[Elkridge, Maryland|Elkridge]]<br />[[Relay, Maryland|Relay]]
|1915
|Concrete arch bridge refurbished in 1952<ref>{{cite web |url=http://bridgehunter.com/md/baltimore/100000030010010/ |title=Patapsco River Bridge |website=bridgehunter.com |date= |access-date= }}</ref>
|-
|[[File:Thomas-viaduct-2011.jpg|alt=|200x200px]]
|[[Thomas Viaduct]]
|[[Baltimore and Ohio Railroad|B&O]] [[Capital Subdivision]]
|[[Elkridge, Maryland|Elkridge]]<br />[[Relay, Maryland|Relay]]
|1835
|World's largest multiple arched bridge. Named after [[Philip E. Thomas]].<ref>{{cite web |url=https://dnr.maryland.gov/publiclands/Pages/central/PatapscoValley/Thomas-Viaduct.aspx |title=Thomas Viaduct |website=dnr.maryland.gov |date= |access-date=29 March 2024 }}</ref>
|-
|
|I-95 bridge
|{{jct|state=MD|I|95}}
|[[Elkridge, Maryland|Elkridge]]<br />[[Relay, Maryland|Relay]]
|1968
|
|-
|
|Gun Road bridge
|Gun Road
|[[Relay, Maryland|Relay]]
|
|[[Patapsco Valley State Park]] access only
|-
|[[File:Patapsco Swinging Bridge 2020a.jpg|alt=|199x199px]]
|[[Patapsco Swinging Bridge]]
|Swinging Bridge Trail
|[[Ilchester, Maryland|Ilchester]]
|2006
|Pedestrian bridge connecting River Road to [[Grist Mill Trail]]
|-
|[[File:Patterson Viaduct Footbridge 2020a.jpg|alt=|199x199px]]
|[[Patterson Viaduct]]
|[[Grist Mill Trail]]
|[[Ilchester, Maryland|Ilchester]]
|2006
|Former rail bridge opened 1829, destroyed 1868, and rebuilt 1869; new footbridge built on abutments of prior rail bridge
|-
|[[File:Ilchester Tunnel.JPG|alt=|200x200px]]
|Ilchester Bridge
|[[Old Main Line Subdivision]]
|[[Ilchester, Maryland|Ilchester]]
|1903
|
|-
|[[File:Ilchester Road Bridge 2020.jpg|alt=|199x199px]]
|Ilchester Road bridge
|Ilchester Road
|[[Ilchester, Maryland|Ilchester]]
|
|Known as Heartbeat Bridge in local folklore.<ref>{{Cite web |date= |title=Haunted Ellicott City |url=http://www.ellicottcity.net/tourism/haunted/ |archive-url=https://web.archive.org/web/20060828130935/http://www.ellicottcity.net/tourism/haunted/ |archive-date=28 August 2006 |access-date=26 March 2024 |website=Historic Ellicott City, MD }}</ref>
|-
|[[File:Railroad bridge at entrance to ellicott city.jpg|alt=|200x200px]]
|Main Street Bridge
|{{jct|state=MD|MD|144|name1=}}
|[[Ellicott City, Maryland|Ellicott City]]<br />[[Oella, Maryland|Oella]]
|1914
|
|-
|
|Baltimore National Pike Bridge
|{{jct|state=MD|US|40|name1=}}
|[[Ellicott City, Maryland|Ellicott City]]<br />[[Catonsville, Maryland|Catonsville]]
|1936
|Reconstructed using original arches in 2014<ref>{{cite web |url=http://bridgehunter.com/md/baltimore/100000030109010/ |title=US40 Patapsco River Bridge |website=bridgehunter.com |date= |access-date= }}</ref>
|-
|
|I-70 bridge
|{{jct|state=MD|I|70}}
|[[Ellicott City, Maryland|Ellicott City]]<br />[[Catonsville, Maryland|Catonsville]]
|1966
|
|-
|
|Hollifield Bridge
|Old Frederick Road
|[[Daniels, Maryland|Daniels]]
|1934
|
|-
|[[File:Daniels Area 78.JPG|200x200px]]
|Daniels bridge
|[[Old Main Line Subdivision]]
|[[Daniels, Maryland|Daniels]]
|
|
|-
|
|Eureka bridge
|[[Old Main Line Subdivision]]
|[[Daniels, Maryland|Mt. Airy]]
|
|
|-
|
|MD 125 bridge
|{{jct|state=MD|MD|125|name1=}}
|[[Woodstock, Maryland|Woodstock]]
|1981
|
|-
! colspan="6" |Patapsco River North Branch-South Branch confluence
|-
|}

==See also==
* [[Patapsco Vallis]], a valley on [[Mars]] named after the river in Maryland
* [[Bloede's Dam]]
* [[List of Maryland rivers]]
* [[List of parks in the Baltimore–Washington metropolitan area]]
* [[Liberty Reservoir]]

==References==
{{Reflist}}
{{Refbegin}}
* [http://archive.chesapeakebay.net/wspv31/(puh4pm45qslzcozj0vnsqo45)/WspAbout.aspx?basno=17&topic=5 Chesapeake Bay Program Watershed Profile]: Patapsco/Back River {{Dead link|date=January 2010}}
* [https://web.archive.org/web/20060526105551/http://www.dnr.state.md.us/publiclands/central/patapscovalley.html Patapsco Valley State Park]
* {{GNIS|597875|Patapsco River}}
{{Refend}}

==External links==
{{Commons category}}
* [http://mddnr.chesapeakebay.net/wsprofiles/surf/prof/patback_profmap.html Maryland DNR's Surf Your Watershed] {{Webarchive|url=https://web.archive.org/web/20060523041040/http://mddnr.chesapeakebay.net/wsprofiles/surf/prof/patback_profmap.html |date=23 May 2006 }}: Patapsco/Back River
* [http://www.americanrivers.org/ American Rivers, a nonprofit conservation organization]
* [http://www.mpa.state.md.us/ Maryland Port Administration] {{Webarchive|url=https://web.archive.org/web/20100201133823/http://www.mpa.state.md.us/ |date=1 February 2010 }}
* [http://bluewaterbaltimore.org/ Blue Water Baltimore, formed in 2010 from a merger of the Gwynns Falls, Jones Falls, Herring Run, and Baltimore Harbor Watershed associations, and the Baltimore Harbor Waterkeeper]
* [http://www.patapscoheritagegreenway.org Patapsco Heritage Greenway]
* [https://web.archive.org/web/20161003134034/http://rockbuilding.org/ Patapsco River Rock Building]

{{Maryland waters}}
{{Patapsco Valley}}

{{Authority control}}

[[Category:Patapsco River| ]]
[[Category:Rivers of Anne Arundel County, Maryland]]
[[Category:Bodies of water of Baltimore]]
[[Category:Rivers of Carroll County, Maryland]]
[[Category:Rivers of Howard County, Maryland]]
[[Category:Rivers of Maryland]]
[[Category:Tributaries of the Chesapeake Bay]]