Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,617,316 residents in 2007[1] and a land area of 68,667 square miles (177,847 kmē),[4] Oklahoma is the 28th most populous and 20th-largest state. The state's name is derived from the Choctaw words okla and humma, meaning "red people",[5] and is known informally by its nickname, The Sooner State. Formed from the Indian Territory on November 16, 1907, Oklahoma was the 46th state to enter the union. Its citizens are known as Oklahomans, and its capital and largest city is Oklahoma City. A major producer of natural gas, oil and food, Oklahoma relies on an economic base of aviation, energy, telecommunications, and biotechnology.[6] It has one of the fastest growing economies in the nation, ranking among the top states in per capita income growth and gross domestic product growth.[7][8] Oklahoma City and Tulsa serve as Oklahoma's primary economic anchors, with nearly 60 percent of Oklahomans living in their metropolitan statistical areas.[9] The state holds a mixed record in education and healthcare, and its largest universities participate in the NCAA and NAIA athletic associations, with two collegiate athletic departments rated among the most successful in American history.