Question: Ninemile Island is in which region of the USA?

full_context: Document 1: Cogley Island: Cogley Island is an alluvial island in the Allegheny River in North Buffalo Township, Armstrong County in the U.S. state of Pennsylvania. The island is situated across from Ford City and Manorville boroughs.
Document 2: Tionesta Creek: Tionesta Creek is a tributary of the Allegheny River in Forest, Clarion, Warren, McKean, and Elk Counties in Pennsylvania in the United States. Together with its West Branch, Tionesta Creek is long, flows generally south, and its watershed is in area.
Document 3: Nicholson Island (Pennsylvania): Nicholson Island is an alluvial island in the Allegheny River in South Buffalo Township, Armstrong County in the U.S. state of Pennsylvania. The island is situated across from Bethel Township.
Document 4: Deer Creek (Allegheny River tributary): Deer Creek is a tributary of the Allegheny River located in both Allegheny and Butler counties in the U.S. state of Pennsylvania.
Document 5: Jacks Island (Pennsylvania): Jacks Island is an alluvial island in the Allegheny River. Its southwestern half lies in the city of Lower Burrell, while its northeastern half lies in Allegheny Township, in Westmoreland County in the U.S. state of Pennsylvania. The island is situated across from Harrison Township in Allegheny County.
Document 6: Cheat River: The Cheat River is a tributary of the Monongahela River in eastern West Virginia and southwestern Pennsylvania in the United States. Via the Ohio River, the Cheat and Monongahela are part of the Mississippi River watershed. Owing to the ruggedness of the surrounding Allegheny Mountains, the Cheat remains largely remote with few settlements or developments along its banks. Its headwaters are in the Cheat-Potomac Ranger District of the Monongahela National Forest.
Document 7: Pucketa Creek: Pucketa Creek is a tributary of the Allegheny River located in both Allegheny and Westmoreland counties in the U.S. state of Pennsylvania.
Document 8: Ross Island (Pennsylvania): Ross Island is an alluvial island in the Allegheny River in Manor Township, Armstrong County in the U.S. state of Pennsylvania. The island is situated across from Cadogan and North Buffalo townships.
Document 9: Cowanshannock Creek: Cowanshannock Creek (the eastern section is sometimes referred to as the North Branch Cowanshannock Creek) is a tributary of the Allegheny River in Armstrong and Indiana counties, Pennsylvania in the United States.
Document 10: Ninemile Island (Pennsylvania): Ninemile Island is an alluvial island in the Allegheny River in the city of Penn Hills, Pennsylvania. It lies southeast of, and parallel to the larger Sycamore Island, which lies in the borough of Blawnox, Allegheny County in the U.S. state of Pennsylvania.
Document 11: Murphy Island (Pennsylvania): Murphy Island (also known as Donley Island) is a privately owned alluvial island in the Allegheny River in Gilpin Township, Armstrong County in the U.S. state of Pennsylvania. The island is situated across from South Buffalo Township.
Document 12: French Creek (Allegheny River tributary): French Creek (also known as the Venango River) is a tributary of the Allegheny River in northwestern Pennsylvania and western New York in the United States.
Document 13: Allegheny River: The Allegheny River (/ ˌæləˈɡeɪni / AL - ə - GAY - nee) is a principal tributary of the Ohio River; it is located in the Eastern United States. The Allegheny River joins with the Monongahela River to form the Ohio River at the ``Point ''of Point State Park in Downtown Pittsburgh, Pennsylvania. The Allegheny River is, by volume, the main headstream of the Ohio River.
Document 14: Sixmile Island (Pennsylvania): Sixmile Island is an alluvial island in the Allegheny River in Allegheny County in the U.S. state of Pennsylvania. It is part of O'Hara Township, and lies across the river from Pittsburgh.
Document 15: List of crossings of the Monongahela River: This is a complete list of current bridges and other crossings of the Monongahela River starting from Pittsburgh, Pennsylvania, where the river helps to form the headwaters of the Ohio River, and ending in Fairmont, West Virginia, where the West Fork River and Tygart Valley River combine to form the Monongahela.
ground_truth: Eastern United States
sub_queries: Ninemile Island >> located on terrain feature Answer: Allegheny River
where is Allegheny River located on a map Answer: Eastern United States