Winchester is an unincorporated community in Douglas County, Oregon, United States. It is located four miles north of Roseburg on Interstate 5 and the North Umpqua River Winchester was laid out in 1850 by surveyor Addison R. Flint, who was part of an Umpqua exploring expedition from San Francisco. The town was named for one of two brothers named Winchester who took part in the expedition, probably Heman Winchester, who was the expedition's captain. Winchester was the largest settlement in the Umpqua Valley for many years and the county seat until 1854, when it was moved to Roseburg. Winchester post office was established in 1851, and Flint served as the first postmaster. The community was incorporated as a city by the Oregon Legislative Assembly on February 20, 1891. Winchester Dam in Winchester, constructed in 1890, is on the National Register of Historic Places.