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. Sullivan City was named for Captain Ed Sullivan, a World War veteran, who owned a ranch. The town was formally opened in 1908. In 1911, the town was incorporated with Sam Hargrove as Mayor. William Jennings Bryan purchased land in the area in 1910, and he established a store and filling station.

Part of Ed Sullivan’s ranch became a loading station on Missouri Pacific Railroad in 1927. The community had 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. A colonia called Rodriguez developed outside Sullivan City, and by 1986 it had grown to a population of 1,013 and 225 dwellings. In 1990, Sullivan City had an estimated population of 2,371.

Sullivan City is located in the County of Hidalgo, alongside the Rio Grande at the southern tip of Texas. The County of Hidalgo, along with Willacy, Cameron, and Starr Counties comprise the Lower Rio Grande Valley Region of Texas, referred as “the Valley”. The Valley serves as an international border between the United States and Mexico with 15 existing points of entry. On the eastern border of the Valley lies the Gulf of Mexico and on the southern border, the Rio Grande. Sullivan City is approximately 57 miles west of the City of Harlingen, 82 miles northwest of the City of Brownsville, 23 miles west of McAllen and 23 miles northwest of the City of Reynosa, in the state of Tamaulipas, Mexico.

Today, City officials that have responsibility for the administration of Sullivan City include the City Mayor, City Commissioners, and City Manager. The Mayor is the presiding officer of the City Council and is recognized as the head of the city government. Appointed by the Mayor and Council, the City Manager is the chief administrative and executive officer of the city. The City Manager has a responsibility to the council for the proper administration of all the affairs of the City. The City Council requires a quorum to do business and the affirmative vote of members of the city council is necessary to adopt any ordinance, resolution, appointment, or other official action. City Council considers the welfare and interests of Sullivan.