Rio Grande City, the county seat of Starr County and one of the oldest settlements in South Texas, is on the Rio Grande 100 miles from both Brownsville and Laredo in the extreme south central part of the county. It is an international port of entry connected by bridge to Camargo, Tamaulipas. The site was part of the Carnestolendas Ranch, established in 1762 by José Antonio de la Garza Falcón in the Spanish colony of José de Escandón. The ranch later belonged to Henry Clay Davis, an adventurous Kentuckian who survived the Mier expedition and formed the present town from Davis Landing or Rancho Davis in 1847 after marrying María Hilaria de la Garza, the granddaughter of Francisco de la Garza Martínez. Davis had acquired the land upon Garza Falcón's death. He designed the port with broad straight streets, on the model of the capital city, Austin. The establishment of Fort Ringgold in 1848, immediately adjacent to the town, assured its growth and permanence. The town received a post office in 1849; in 1895 the name of the post office changed from Rio Grande City to Riogrande, the name under which it now operates. Despite the town's isolation and lack of transportation facilities for most of its history, external influences have affected it significantly. During the nineteenth century Rio Grande City had an active passenger and cargo ship trade with New Orleans and flourished as a cattle center. Frequent encroachments from Mexico, most notably those of Juan Cortina in 1859, forced the community to rely often on the Texas Rangers and the United States Army for protection. In 1884 the town had a population of 900, a doctor, two lawyers, a saloon, three carpenters, three grocers, nine general stores, a wagon maker, a druggist, two blacksmiths, two churches, a district school, a tailor, a furniture maker, a cornmill, and a hotel. By 1896 Rio Grande City had a population of 1,800, and by 1914 it had a bank and 2,100 residents.
Race relations were so tense that they helped give rise to the Rio Grande City Riot of 1888, in which the Mexican population was pitted against the White-controlled sheriff's office. In another racial incident, members of the Black Ninth United States Cavalry fired toward the town in 1899, amid reports of a civilian attack on the garrison. A series of investigations produced inconclusive findings but culminated in the withdrawal of the troops (see FORT RINGGOLD). In 1925 Rio Grande City reported a population of 3,000, but by 1931 it had 2,283 residents and ninety businesses. In August 1926 residents voted for incorporation, but the city went into debt during the Great Depression, and residents voted to unincorporate in May 1933 to avoid repayment of the sizable debt accrued for improvements to the town. Throughout the 1940s the population remained at 2,500. In 1954 it was 3,992. Rio Grande City continued to grow in the 1960s and by 1964 had a population of 6,435 and 130 businesses. By 1974 the population had fallen off slightly to 5,720, where it remained through the 1980s. In 1990 it was 9,891. The population grew to 11,923 in 2000. Hurricanes struck the city in 1919 and 1967. In 1967 the United Farm Workers Union sought federal protection from Texas Rangers in an unsuccessful attempt to organize melon pickers. An oil and gas boom of the 1930s broadened the town's limited economic base, which includes exports to Mexico, brickmaking, food production, and tourism. Rio Grande City has several historic structures, including Fort Ringgold, La Borde House, and a replica of the shrine of Our Lady of Lourdes. The city voted to reincorporate in 1993.