Amarillo ( AM-ə-RIL-oh; Spanish for "yellow") is a city in the U.S. state of Texas and the seat of Potter County. It is the 14th-most populous city in Texas and the most populous city in the Texas panhandle. A portion of the city extends into Randall County. The estimated population of Amarillo was 200,393 as of April 1, 2020, comprising nearly half of the population of the panhandle. The Amarillo metropolitan area had an estimated population of 308,297 as of 2020. The city of Amarillo, originally named Oneida, is situated in the Llano Estacado region. The availability of the railroad and freight service provided by the Fort Worth and Denver City Railroad contributed to the city's growth as a cattle-marketing center in the late 19th century. Amarillo was once the self-proclaimed "Helium Capital of the World" for having one of the country's most productive helium fields. The city is also known as "The Yellow Rose of Texas" (as the city takes its name from the Spanish word for yellow), "Yellow City" for its name, and "Rotor City, USA" for its V-22 Osprey hybrid aircraft assembly plant. Amarillo operates one of the largest meat-packing areas in the United States. Pantex, the only nuclear weapons assembly and disassembly facility in the country, is also a major employer. The location of this facility also gave rise to the nickname "Bomb City".