a city of Washington county, Pennsylvania, U.S.A., on the Monongahela river, 31 m. by rail S. of Pittsburg. Pop. (1890), 4096; (1900), 5173 (71 foreign-born and 345 negroes); (1910) 7598. It is served by the Pennsylvania and the. Pittsburg & Lake Erie railways, and by electric railways to Pittsburg and Washington, Pa. Monongahela is in a coal region, and the mining of coal is its principal industry. It was laid out as a town in 1792 by Joseph Parkinson, and named by him Williamsport; but it was commonly known as Parkinson's Ferry until 1833, when it was incorporated as a borough. Four years later the present name was adopted, and in 1873 Monongahela was chartered as a city. It was here that the Whisky Insurrection convention met on the 14th of August 1794.