When the mail route from the northwestern Iowa cities of Pocahontas to Humboldt was established in May 1878, Ellen Van Alstine was appointed postmistress of a the Blooming Prairie Post Office a mile north of present-day Gilmore City. When the railroad was constructed a mile south of Blooming Prairie, the post office was transferred a mile south and known as the Gilmore City Post Office as of August 3, 1882. The present facility opened on July 1, 1957, constructed as a stand-alone post office at a cost of $8,000.