Although Tenmile is unincorporated, it has a post office by the same name. The ZIP code is 97481.
Tenmile Post Office was so-named because a pioneer drove his cattle from Happy Valley in Douglas County to an area now known as Tenmile Valley. The distance between the two places was about 10 miles. The post office was established in 1870 as "Ten Mile" and changed to "Tenmile" in 1918.