Omaha ( OH-mə-hah) is the most populous city in the U.S. state of Nebraska and the county seat of Douglas County. It is located in the Midwestern United States along the Missouri River, about 10 mi (15 km) north of the mouth of the Platte River. The nation's 40th-most populous city, Omaha had a population of 486,051 as of the 2020 census. It is the anchor of the eight-county Omaha–Council Bluffs metropolitan area, which extends into Iowa and is the 58th-largest metro area in the United States, with a population of 967,604. Furthermore, the greater Omaha–Council Bluffs–Fremont combined statistical area had 1,004,771 residents in 2020. Omaha's pioneer period began in 1854, when the city was founded by speculators from neighboring Council Bluffs, Iowa. The city was founded along the Missouri River, and a crossing called Lone Tree Ferry earned the city its nickname, the "Gateway to the West". Omaha introduced this new West to the world in 1898, when it played host to the World's Fair, dubbed the Trans-Mississippi Exposition. During the 19th century, Omaha's central location in the United States spurred the city to become an important national transportation hub. Throughout the rest of the 19th century, the transportation and jobbing sectors were important in the city, along with its railroads and breweries. In the 20th century, the Omaha Stockyards, once the world's largest, and its meatpacking plants gained international prominence. Omaha is the home to the headquarters of four Fortune 500 companies: Berkshire Hathaway, Kiewit Corporation, Mutual of Omaha, and Union Pacific Corporation. Other companies headquartered in the city include First National Bank of Omaha, Gallup, Inc., Green Plains, Intrado, Valmont Industries, Werner Enterprises, and three of the nation's ten largest architecture and engineering firms (DLR Group, HDR, Inc., and Leo A Daly). Notable cultural institutions include the Henry Doorly Zoo and Aquarium, Old Market, Durham Museum, Lauritzen Gardens, and annual College World Series. Modern Omaha inventions include the Reuben sandwich; cake mix, developed by Duncan Hines; center-pivot irrigation; Raisin Bran; the first ski lift in the U.S.; the Top 40 radio format as first used in the U.S. at Omaha's KOWH Radio; and the TV dinner.