Allegheny Islands State Park is a Pennsylvania state park in Harmar Township,

Allegheny County Allegheny County () is a County (United States), county in the Commonwealth (U.S. state), Commonwealth of Pennsylvania. It is located in Southwestern Pennsylvania. As of the 2020 census, the population was 1,250,578, making it the state's seco ...

, Pennsylvania in the United States. The undeveloped park is composed of three alluvial islands located in the middle of 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 ...

northeast of Pittsburgh. The islands are just north of the boroughs of

Oakmont Oakmont is a borough in Allegheny County, in the U.S. state of Pennsylvania. It is a Pittsburgh suburb and part of the Pittsburgh Metro Area. The population was 6,303 as of the 2010 Census. Incorporated as a town in 1889, this Allegheny River c ...

and

Plum A plum is a fruit of some species in ''Prunus'' subg. ''Prunus'.'' Dried plums are called prunes. History Plums may have been one of the first fruits domesticated by humans. Three of the most abundantly cultivated species are not found i ...

, and southwest of Cheswick. ''Note: shows Allegheny River and its islands'' Bridges for the Pennsylvania Turnpike ( Interstate 76) and the Bessemer and Lake Erie Railroad Branch of the

Canadian National Railway The Canadian National Railway Company (french: Compagnie des chemins de fer nationaux du Canada) is a Canadian Class I freight railway headquartered in Montreal, Quebec, which serves Canada and the Midwestern and Southern United States. CN i ...

cross the Allegheny River at the middle island.

Islands

The park land on the islands has a total area of , with two islands downstream of the Allegheny River Lock and Dam Three (officially named the ''C. W. Bill Young Lock and Dam''), and the other island upstream. Twelve Mile Island is the farthest downstream (west) and has a number of houses and buildings on the western four-fifths of the island (the park land is the eastern end). The remaining two islands are both uninhabited and have no structures on them. They were originally one island named Fourteen Mile Island, but were split into two parts by the construction of the dam. Today the name Fourteen Mile Island is given to the middle island, just downstream (west) of the dam, and it is the site of the highway and railroad bridges. According to the USGS GNIS, the last island (which was once part of Fourteen Mile Island) is unnamed (although it is still labeled "Fourteen Mile Island" on the U.S. Army Corps of Engineers navigation maps of the Allegheny River.) This unnamed island is the easternmost and the only one upstream of the dam. There are also five to seven

shoal In oceanography, geomorphology, and geoscience, a shoal is a natural submerged ridge, bank, or bar that consists of, or is covered by, sand or other unconsolidated material and rises from the bed of a body of water to near the surface. It ...

s near the islands, which are occasionally exposed. Twelve Mile Island and Fourteen Mile Island are named for their distances, and , up the Allegheny River from the

confluence In geography, a confluence (also: ''conflux'') occurs where two or more flowing bodies of water join to form a single channel. A confluence can occur in several configurations: at the point where a tributary joins a larger river (main stem); o ...

of the Allegheny and Monongahela Rivers to form the

Ohio River The Ohio River is a long river in the United States. It is located at the boundary of the Midwestern and Southern United States, flowing southwesterly from western Pennsylvania to its mouth on the Mississippi River at the southern tip of Illino ...

in downtown Pittsburgh. They are two of six alluvial islands in the Allegheny River near Pittsburgh (for comparison, near Pittsburgh the Ohio River has only three islands and the Monongahela River has none). "The large number of islands in the Allegheny is a reflection of the large amount of glacially-derived sediment that was moved by the river."

Facilities

Allegheny Islands State Park was established on December 31, 1980. , it is undeveloped so that there are no facilities, and also no plans for future development. The park can only be accessed by boat. Camping is allowed on the islands and they are open for visits by groups such as the

Boy Scout A Scout (in some countries a Boy Scout, Girl Scout, or Pathfinder) is a child, usually 10–18 years of age, participating in the worldwide Scouting movement. Because of the large age and development span, many Scouting associations have split ...

s and Venture Outdoors. Allegheny Islands State Park is administered from the Region 2 Office in Prospect, Pennsylvania.

Nearby state parks

The following state parks are within of Allegheny Islands State Park: * Hillman State Park ( Washington County) * Keystone State Park ( Westmoreland County) * Point State Park (Allegheny County)

References

External links

{{Authority control Allegheny Islands Parks in the Pittsburgh metropolitan area Islands of the Allegheny River in Pennsylvania Protected areas established in 1980 Parks in Allegheny County, Pennsylvania Islands of Allegheny County, Pennsylvania 1980 establishments in Pennsylvania Protected areas of Allegheny County, Pennsylvania