www.dallascityhall.com Night view of Elm Street, January 1942 Dallas ( /ˈdæləs/) is the third-largest city in the state of Texas and the ninth-largest in the United States. The Dallas-Fort Worth metroplex is the largest metropolitan area in the South and fourth-largest metropolitan area in the United States. Divided between Collin, Dallas, Denton, Kaufman, and Rockwall counties, the city had a population of 1,197,816 in 2010, according to the United States Census Bureau. The city is the largest economic center of the 12-county Dallas–Fort Worth–Arlington metropolitan area (the DFW MSA) that according to the March 2010 U.S. Census Bureau release, had a population of 6,371,773. The metroplex economy is the sixth largest in the United States, with a 2010 gross metropolitan product of $374 billion. Dallas was founded in 1841 and was formally incorporated as a city in February 1856. The city's economy is primarily based on banking, commerce, telecommunications, computer technology, energy, healthcare and medical research, transportation and logistics. The city is home to the third largest concentration of Fortune 500 companies in the nation. Located in North Texas and a major city in the American South, Dallas is the main core of the largest inland metropolitan area in the United States that lacks any navigable link to the sea. The city's prominence arose from its historical importance as a center for the oil and cotton industries, and its position along numerous railroad lines. With the advent of the interstate highway system in the 1950s and 1960s, Dallas became an east/west and north/south focal point of the interstate system with the convergence of four major interstate highways in the city, along with a fifth interstate loop around the city. Dallas developed a strong industrial and financial sector, and a major inland port, due largely to the presence of Dallas/Fort Worth International Airport, one of the largest and busiest airports in the world. In the latest rankings released on September 14, 2011, Dallas was rated as an Alpha- world city by the Globalization and World Cities Study Group & Network and is the only city in the South Central and Southwest regions to achieve that status. Dallas is also ranked 14th in world rankings of GDP by the Organization for Economic Co-operation and Development.