Amarillo is the 14th-largest city in the U.S. state of Texas, the largest in the Texas Panhandle, and the seat of Potter County. Amarillo was originally named Oneida and it 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 the city's growth as a cattle marketing center in the late 19th century.The city 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). Also crowned Beef City by Amarillo group Lockjaw for the city's growth as a cattle marketing center in the late 19th century. and former beef industry IBP now owned by Tyson Foods and most recently 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 attractions Cadillac Ranch and Big Texan Steak Ranch were located on the former U.S. Highway 66, which passes through the city.