The term 'Allegheny River City on the' is completed by two crossword solutions: OLEAN (5 letters) and OHIO (4 letters). OLEAN is a city located in Cattaraugus County, New York, on the Allegheny River. It is the largest city in the county and is home to St. Bonaventure University. OHIO is a state located in the Midwestern United States. It is bordered by Lake Erie to the north and the Allegheny River to the east.