Sumpter is a city in Baker County, Oregon, United States. The population was 204 at the 2010 census. Sumpter is named after Fort Sumter by its founders. The name was inspired by a rock as smooth and round as a cannonball, which reminded a local resident of the American Civil War and Fort Sumter.

Baker County is one of the 36 counties in the U.S. state of Oregon. As of the 2020 census, the population was 16,668. The county seat and largest city is Baker City. The county was organized on September 22, 1862, when a portion of Wasco County was partitioned off. The new county's area was reduced in 1864 when Union County was partitioned off, and again in 1887 when Malheur County was partitioned off. The county's lines were last adjusted in 1901 when a parcel was added to the county.