Sullivan City is off U.S. Highway 83 and Farm Road 886 a mile east of the Starr county line in extreme southwestern Hidalgo County. The site, part of Ed W. Sullivan's ranch, became a loading station on the Missouri Pacific Railroad in 1927. The community had a population of 250, a post office, and fifteen businesses by 1930. By 1947 Sullivan City had nine businesses and a population of 250. During the 1950s the population remained constant at 250, but the number of businesses increased to twenty. In 1974 the population was 350. In 1990 Sullivan City had an estimated population of 2,371 and no businesses. A colonia called Rodriguez developed outside Sullivan City, and by 1986 it had grown to a population of 1,013 and 225 dwellings. In 2000 the population was 3,998.