According to William Gladstone Steel, the community was founded in 1888 by John B. Dalley (other sources have the spelling as "Dulley"[3]), who named it after Charles Sumner, a Massachusetts senator who died in 1874.[4] Sumner post office was established in 1874, so according to Oregon Geographic Names, Steel must have been incorrect about the 1888 founding date.[4] Dalley was the first postmaster, and the office closed in 1961.[4] In 1915, Sumner had a population of 100.[5] As of 1990, the community had one store.[5]