Missouri (State of Missouri) is in the Midwest region of the United States, with a land area of 180,546 square kilometers and a population of 6.08 million. The terrain is mainly dominated by plains and hills. Its zip code is MO and its capital is Jefferson City. Important airports in Missouri are: St. Louis Lambert International Airport (STL), which is the transit center for American Airlines, as well as Kansas City International Airport (MCI) and Springfield Airport (SGF). The area code for Missouri is: 314 - 417 - 573 - 636 - 660 - 816. The zip codes for important cities are as follows: Jefferson City zip codes are 65101-65111. The zip code for Saint Louis is 63101-63199. The ZIP code for Kansas City is 64101-64999. The zip code for Rolla is 65401-65409.