Harlem, OhioHarlem is an unincorporated community in Harlem [Township, Delaware County, Ohio|Harlem Township], Delaware [County, Ohio|Delaware County], in the U.S. state of Ohio.HistoryHarlem was platted in 1849 and named for its location within Harlem Township. A post office was established at Harlem in 1830, and remained in operation until 1907.