Warren, a borough and the county-seat of Warren county, Pennsylvania, U.S.A., on the N. side of the Allegheny river at the mouth of the Conewango river, about 35 m. N.E. of Titusville. Pop. (1880) 2810; (1890) 433 2; (1900) 8043, of whom 1529 were foreign-born; (1906, estimate) 10,647. The foreign element is largely Swedish, Danish and Slavish. Warren is served by the Pennsylvania and the Dunkirk, Allegheny Valley & Pittsburg railways, and by electric railway to Jamestown, New York. Among the public buildings and institutions are the county court house, a state hospital for the insane (established 1873), a Y.M.C.A. building and a state armoury. Warren is situated at the southern foot of a high sheer ridge, in a region rich in oil and natural gas; the borough ships and refines oil, and has various manufactures. The total value of its factory product in 1905 was $5,976,905 (62.4% more than in 1900), of which $3,038,894 was the value of refined oil and $1,220,165 the value of foundry and machine-shop products. The borough owns and operates the water-works and the electric lighting plant. The town site of Warren was laid out by commissioners appointed by Governor Thomas Mifflin in 1795, and Warren was incorporated as a borough in 1832; it was named in honour of Joseph Warren, the American patriot. In 1895 part of Glade township was annexed.
See J. S. Schenck and W. S. Rann, History of Warren County, Pennsylvania (Syracuse, N.Y., 1887).