Brownsville is a borough in Fayette County, Pennsylvania, United States, founded in 1785 and located south of Pittsburgh along the Monongahela River. In the 19th century, the borough became an industrial center, transportation hub, outfitting center, and river boat-building powerhouse. It was a gateway city for emigrants heading west to the Ohio Country, Northwest Territory and beyond on the various Emigrant Trails to the far west from its founding until well into the 1850s.
Brownsville became a major center for building steamboats through the 19th century, producing 3,000 boats by 1888. It exceeded nearby Pittsburgh in population and economy until well into the 1850s, when the railroads connected Pittsburgh with Kanesville, Iowa on the Missouri River in the Midwest, and established a major traffic route. Being bypassed by the major railroad route permanently affected Brownsville's economy and made it subsidiary to Pittsburgh.
The borough developed in the late 19th century as a railroad yard and coking center, with other industries related to the rise of steel in the Pittsburgh area. It reached a peak of population of more than 8,000 in 1940. Postwar development occurred in suburbs, as was typical of the time. The restructuring of the railroad and steel industries caused a severe loss of jobs and population in Brownsville, beginning in the 1970s. The borough has a population of 2331 as of 2010.