The Allegheny River Lock and Dam No. 4 in

Harrison Township, Allegheny County, Pennsylvania Harrison Township is a township in Allegheny County in the U.S. state of Pennsylvania. The population was 10,169 at the 2020 census. Pennsylvania Route 28 passes through Harrison Township connecting Kittanning to the northeast and Pittsburgh ...

, is a

lock Lock(s) may refer to: Common meanings *Lock and key, a mechanical device used to secure items of importance *Lock (water navigation), a device for boats to transit between different levels of water, as in a canal Arts and entertainment * ''Lock ...

that was built 1920-1927, and opened in 1927, 24.2 miles upstream from the mouth of the river in Pittsburgh. The lock and dam were built by the U.S. Army Corps of Engineers as a part of an extensive system of locks and dams to improve navigation along the

Allegheny River The Allegheny River ( ) is a long headwater stream of the Ohio River in western Pennsylvania and New York (state), New York. The Allegheny River runs from its headwaters just below the middle of Pennsylvania's northern border northwesterly into ...

. It is located about 24.2 Miles up the

from the

Point Point or points may refer to: Places * Point, Lewis, a peninsula in the Outer Hebrides, Scotland * Point, Texas, a city in Rains County, Texas, United States * Point, the NE tip and a ferry terminal of Lismore, Inner Hebrides, Scotland * Point ...

Downtown Pittsburgh Downtown Pittsburgh, colloquially referred to as the Golden Triangle, and officially the Central Business District, is the urban downtown center of Pittsburgh. It is located at the confluence of the Allegheny River and the Monongahela River whose ...

. Also, it is about 6 Miles down the Allegheny from the mouth of the

Kiskiminetas River The Kiskiminetas River (commonly referred to as the Kiski by locals) is a tributary of the Allegheny River, approximately long, in Western Pennsylvania in the United States. The region stretching from the northern side of Harmar Township, Penns ...

.https://www.lrp.usace.army.mil/Portals/72/docs/navigation/AlleghenyRiverNavigationChart.pdf Upriver, Allegheny Pool No. 4 has an average water elevation of 745.4 feet above sea level and extends about 6.2 miles upriver to

Allegheny River Lock and Dam No. 5 Allegheny River Lock and Dam No. 5 is a historic lock and fixed-crest dam complex located at Gilpin Township and South Buffalo Township in Armstrong County, Pennsylvania. It was built between 1920 and 1927 by the United States Army Corps of Engi ...

. Downriver, Allegheny Pool No. 3 has an average water elevation of 734.5 feet above sea level and extends about 9.7 miles downriver to

Allegheny River Lock and Dam No. 3 C.W. Bill Young Lock and Dam (formerly known as Allegheny River Lock and Dam No. 3) in Harmar Township, Allegheny County, Pennsylvania, and Plum, Pennsylvania, is a lock that was built in 1932. The lock and fixed-crest dam were built by the U.S. ...

. Thus Lock No. 4 lifts and lowers boats about 10.9 feet between the pools. It has a single lock and a

fixed-crest dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, tap water, human consumption, Industri ...

, keeping the river depth at least 9 feet in the pool above the dam. The amount of water that flows over the dam is not controlled locally, so it does not provide flood control, but it does help provide water to municipalities. Traffic through the lock was about 1.8 million tons in 1998, including shipments of coal, petroleum, sand and gravel, ore, steel, chemicals, fertilizer, salt, flour, lime, and slag. It was listed on the

National Register of Historic Places The National Register of Historic Places (NRHP) is the United States federal government's official list of districts, sites, buildings, structures and objects deemed worthy of preservation for their historical significance or "great artistic v ...

on April 21, 2000.

References

{{Clear Dams on the Allegheny River Dams in Pennsylvania Buildings and structures in Allegheny County, Pennsylvania Dams on the National Register of Historic Places in Pennsylvania Locks on the National Register of Historic Places in Pennsylvania Dams completed in 1927 Transport infrastructure completed in 1927 Moderne architecture in Pennsylvania 1927 establishments in Pennsylvania National Register of Historic Places in Allegheny County, Pennsylvania Transportation buildings and structures in Allegheny County, Pennsylvania