Texas Triangle in the context of "San Antonio"

Houston is the most populous city in the U.S. state of Texas and the Southern United States. It is the fourth-most populous city in the United States, with a population of 2.3 million at the 2020 census. The Greater Houston metropolitan area, at 7.8 million residents, is the fifth-most populous metropolitan area in the nation and second-most populous in Texas. Located in Southeast Texas near Galveston Bay and the Gulf of Mexico, Houston is the seat of Harris County. Covering a total area of 640.4 square miles (1,659 km), it is the ninth largest city in the country and the largest whose municipal government is not consolidated with a county, parish, or borough. Although primarily located within Harris County, portions of the city extend into Fort Bend and Montgomery counties. Houston also functions as the southeastern anchor of the Texas Triangle megaregion.

Houston was founded by land investors on August 30, 1836, at the confluence of Buffalo Bayou and White Oak Bayou (a point now known as Allen's Landing) and incorporated as a city on June 5, 1837. The city is named after former General Sam Houston, who was president of the Republic of Texas and had won Texas's independence from Mexico at the Battle of San Jacinto 25 miles (40 km) east of Allen's Landing. After briefly serving as the capital of the Texas Republic in the late 1830s, Houston grew steadily into a regional trading center for the remainder of the 19th century. The 20th century brought a convergence of economic factors that fueled rapid growth in Houston, including a burgeoning port and railroad industry, the decline of Galveston as Texas's primary port following a devastating 1900 hurricane, the subsequent construction of the Houston Ship Channel, and the Texas oil boom. In the mid-20th century, Houston's economy diversified, as it became home to the Texas Medical Center—the world's largest concentration of healthcare and research institutions—and NASA's Johnson Space Center, home to the Mission Control Center.

Greater Houston, designated by the United States Office of Management and Budget as Houston–Pasadena–The Woodlands, is the fifth-most populous metropolitan statistical area in the United States, encompassing ten counties along the Gulf Coast in Southeast Texas. With a population of 7,824,643 in 2025,

The region of approximately 10,000 square miles (26,000 square kilometers) centers on Harris County, the third-most populous county in the U.S., which contains the city of Houston, the economic and cultural center of the South with a population of more than 2.3 million as of 2010. Greater Houston is part of the Texas Triangle megaregion along with the Dallas–Fort Worth metroplex, Greater Austin, and Greater San Antonio. Greater Houston also serves as a major anchor and economic hub for the Gulf Coast. Its Port of Houston is the largest port in the United States and the 16th-largest in the world.

Greater San Antonio, officially designated San Antonio–New Braunfels, is an eight-county metropolitan area in the U.S. state of Texas defined by the Office of Management and Budget (OMB). The metropolitan area straddles South Texas and Central Texas and is on the southwestern corner of the Texas Triangle. The official 2020 U.S. census showed the metropolitan area's population at 2,558,143—up from a reported 1,711,103 in 2000—making it the 24th largest metropolitan area in the United States. Downtown Austin and Downtown San Antonio are approximately 80 miles (129 km) apart, and both fall along the Interstate 35 corridor. This combined metropolitan region of San Antonio–Austin has approximately 5.1 million people.

San Antonio–New Braunfels is the third-largest metro area in Texas, after Dallas–Fort Worth–Arlington and Houston–The Woodlands–Sugar Land.

The U.S. state of Texas is divided into 254 counties, more than any other U.S. state. While only about 20% of Texas counties are generally located within the Houston—Dallas—San Antonio—Austin areas, they serve a majority of the state's population with approximately 22,000,000 inhabitants.

Texas was originally divided into municipalities (municipios in Spanish), a unit of local government under Spanish and Mexican rule. When the Republic of Texas gained its independence in 1836, the 23 municipalities became the original Texas counties. Many of these were later divided into new counties. The last county to be initially created was Kenedy County in 1921, but Loving County is the newest organized county; it was first organized in 1893 in an apparent scheme to defraud, abolished in 1897, then reorganized in 1931. Most of these recent counties, especially near the northwest, were created from Bexar County during the 1870s.