[2] The name comes from a Sahaptin language word meaning black hawthorn bush.

[4] Simnasho was the reservation's seat of government, in the form of a Federal agent, until near the end of the 19th century, when the agency headquarters was relocated to the community of Warm Springs.

An 11-member tribal council is the main governing body for the reservation, which is divided into three districts—Simnasho, Agency, and Seekseekqua.

During the 2013–16 term, they are Evaline Patt (vice-chair of the council), Raymond Tsumpti Sr., and Orvie Danzuka.

Warm Springs Chief Delvis Heath is the lifetime council member representing Simnasho.