San Antonio, officially the City of San Antonio, is the seventh-most populous city in the United States, second largest city in the Southern United States, and the second-most populous city in Texas with 1,434,625 residents in 2020. Founded as a Spanish mission and colonial outpost in 1718, the city became the first chartered civil settlement in present-day Texas in 1731. The area was still part of the Spanish Empire, and later of the Mexican Republic. It is the state's oldest municipality, having celebrated its 300th anniversary on May 1, 2018.
The city's deep history is contrasted with its rapid growth over the past few decades. It was the fastest-growing of the top ten largest cities in the United States from 2000 to 2010, and the second from 1990 to 2000. Straddling the regional divide between South and Central Texas, San Antonio anchors the southwestern corner of an urban megaregion colloquially known as the Texas Triangle. The Greater San Antonio and Greater Austin areas are separated from each other by approximately 80 miles along Interstate 35. Both metropolitan regions are expected to form a new metroplex similar to Dallas and Fort Worth.