Columbia is the capital and second largest city of the U.S. state of South Carolina, with a population estimate of 133,451 as of 2018. The city serves as the county seat of Richland County, and a portion of the city extends into neighboring Lexington County. It is the center of the Columbia metropolitan statistical area, which had a population of 767,598 as of the 2010 United States Census, growing to 832,666 by July 1, 2018, according to 2018 U.S. Census estimates. This makes it the 70th largest metropolitan statistical area in the nation, as estimated by the United States Census Bureau as of July 1, 2018. The name Columbia is a poetic term used for the United States, originating from the name of Christopher Columbus. The city is located approximately 13 mi northwest of the geographic center of South Carolina, and is the primary city of the Midlands region of the state. It lies at the confluence of the Saluda River and the Broad River, which merge at Columbia to form the Congaree River. Columbia is home to the University of South Carolina, the state's flagship university and the largest in the state, and is also the site of Fort Jackson, the largest United States Army installation for Basic Combat Training. Columbia is also located 20 miles west of the site of McEntire Joint National Guard Base, which is operated by the U.S. Air Force and is used as a training base for the 169th Fighter Wing of The South Carolina Air National Guard. Columbia is also the location of the South Carolina State House, which is the center of government for the state. In 1860, the city was the location of the South Carolina Secession Convention, which marked the departure of the first state from the Union in the events leading up to the Civil War.