Brownsville is a borough in Fayette County, Pennsylvania, United States, founded in 1785 and located 35 miles (56 km) 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.