The Town of Great Valley, was formed from Olean on April 15, 1818. Burton, now Allegany was taken off in 1831, and Carrolton in 1842. Part of the Allegany Reservation was annexed in 1847. It is an interior town, lying just a little south of the center of Cattaraugus County. Its surface is mountainous and hilly upland. The highest summit, near the southwest corner, is 1300 feet above the river. The Allegany River flows through the southwest corner, receiving the Great Valley Creek as tributary. The main industry is lumbering, with 80% of the surface being covered with forests
Great Valley Station, Killbuck post office, is a hamlet , in the south, on the mouth of Great Valley Creek. Peth is another small named area.
Settlement was commenced at the mouth of Great Valley Creek, by Judge James Green, in 1812. Other early settlers included: Daniel McKay, Judge Benjamin Chamberlin, and --- Hibbard, who located in 1813. Lewis Worcester and Laurin Norton, came in 1814.
The first child born was Ira Green, in 1813; the first death was Mrs. Hibbard, in 1813.
The first school was taught by Joel Fairbanks, at the house of James Green in 1817-1818 . In 1813, the first inn was opened, by James Green, at the mouth of Great Valley Creek; and the first store by Lewis Worcester, in 1815 at Peth . A sawmill was built by James Green in 1812.