Monaca ( mi-NAK-ə) is a borough in Beaver County, Pennsylvania, United States along the Ohio River, 25 miles (40 km) northwest of Pittsburgh. First incorporated as Phillipsburg as the home of the New Philadelphia Society, the name of the borough was changed to Monaca in honor of the Native American Monacatootha. Fire clay is found in large quantities in the vicinity, and there is an Anchor Hocking plant in the town.
The population was 5,737 as of the 2010 Census.
Monaca has a history dating back to the 18th century. The land on which Monaca now stands was granted by the Commonwealth of Pennsylvania by patent, bearing the date September 5, 1787, to Colonel Ephraim Blaine (1741–1804), who served in the Continental Army during the Revolutionary War, from 1778 to 1782 as commissary-general of the Northern Department, and paternal great-grandfather of James G. Blaine. In the patent, this tract was called "Appetite". On August 1, 1813, the land was bought by Francis Helvidi (or Helveti, Helvedi, Helvety), described as a Polish nobleman who was exiled from his native country and immigrated to America. Helvidi, who may have been the first white settler in Monaca, bought the large "Appetite" tract and raised sheep on it, but his venture was unsuccessful. Harmony Society leader George Rapp, one of Helveti's creditors, complained in 1815 "about the risk Helvety is taking with the sheep," and in 1821, the property was sold at Sheriff's sale to Rapp.
In 1822, the beginnings of a town appeared when Stephen Phillips and John Graham purchased the property and established their "extensive boat yards" on the Ohio River there.