On August 17, 1903, Foster Post Office opens. Adam Held serves as the first postmaster. Mail is distributed from a store operated by Joseph Foster located at 52nd Avenue S (formerly Foster Street) and Interurban Avenue S.
On April 30, 1907, the post office closes. Foster was located 9 miles south of Seattle within the city limits of Tukwila on the Duwamish River at the southwest quarter of the northwest quarter Section 14 Township 23 N Range 4 E.