Belpre is a city in Washington County, Ohio, United States, along the Ohio River. The town was originally named Belle Prairie or "Beautiful Prairie. " Part of the Parkersburg-Marietta-Vienna, WV-OH Metropolitan Statistical Area, it is located about 14 miles downriver from Marietta. In 1870 the Baltimore and Ohio Railroad completed the Parkersburg Bridge (CSX) across the river; at 7,140 feet, it was reportedly the longest in the world. The population was 6,441 at the 2010 census. Belpre was the second United States settlement in the Northwest Territory after Marietta. The city is home to the first library established in the Territory. Its public school hired the first female schoolteacher in Ohio.