On January 13, 1903, Humphrey Post Office opens. John W. Reed is appointed the first postmaster. Humphrey, renamed Youngstown on July 19, 1905, is located in present-day West Seattle three miles south of the business district of Seattle within the future city limits.
During 1904, the Seattle Steel Company started manufacturing steel, the first to be produced in King County. The company, owned by William Piggott (1860-1929), was located in Youngstown.
In 1907, Youngstown was annexed to Seattle.