Dallas with a population of 1,279,910 is the third-largest city in Texas and the 8th-largest in the United States. The city is the main economic center of the 12-county Dallas–Fort Worth Metroplex that according to the March 2009 U.S. Census Bureau release had a population of 6,300,006 as of July 2008. The Dallas/Ft. Worth area is the fourth largest and number one fastest-growing (by population) metropolitan area in the United States. Dallas is rated as a beta world city by the Globalization and World Cities Study Group & Network. Founded in 1841 and formally incorporated as a city in February, 1856, the city's economy is primarily based on banking, commerce, telecommunications, computer technology, energy and transportation; only New York City and Houston are home to more Fortune 500 headquarters in the city limits. Located in North Texas and a major city in the American South/Southwest, Dallas is the core of the largest inland metropolitan area in the United States that lacks any navigable link to the sea. The city's prominence despite this comes from its historical importance as a center for the oil and cotton industries, its position along numerous railroad lines, a strong industrial and financial sector, and its status as a major inland port (due largely to the presence of Dallas/Fort Worth International Airport, one of the largest and busiest in the world).