In 1889, Harlem was founded and became known as a trading center for the Fort Belknap Indian Reservation. Located in Smith's General Merchandise Store was the first post office, a shoe box. As time went on, the volume of mail outgrew the box and an empty beer case took its place. The first post office was established in 1890 with John Manning as postmaster. Harlem was named by the officials of the Great Northern Railroad in St. Paul. The station, located in a boxcar, was picked by spinning a globe of the world, while blindfolded, and pointing to an area. This time, the area chosen was in Haarlem (Netherlands).
Harlem is located in the north-central area of Montana, off U.S. Highway 2 between Havre and Malta.