the largest bank holding company in the United States, established national banking operations in South Dakota in 1981 to take advantage of favorable banking regulations. Government spending is another important segment of the state's economy, providing over ten percent of the gross state product. Ellsworth Air Force Base, near Rapid City, is the second-largest single employer in the state. Agriculture has historically been a key component of the South Dakota economy. Although other industries have expanded rapidly in recent decades, agricultural production is still very important to the state's economy, especially in rural areas. The five most valuable agricultural products in South Dakota are cattle, corn (maize), soybeans, wheat, and hogs. Agriculture-related industries such as meat packing and ethanol production also have a considerable economic impact on the state. South Dakota is the sixth leading ethanol-producing state in the nation. Another important sector in South Dakota's economy is tourism. Many travel to view the attractions of the state, particularly those in the Black Hills region, such as historic Deadwood, Mount Rushmore, and the nearby state and national parks. One of the largest tourist events in the state is the annual Sturgis Motorcycle Rally. The five-day event drew over 739,000 attendees in 2015; significant considering the state has a total population of 850,000. In 2006, tourism provided an estimated 33,000 jobs in the state and contributed over two billion dollars to the economy of South Dakota. Transportation South Dakota has of highways, roads, and streets, along with of interstate highways. Two major interstates pass through South Dakota: Interstate 90, which runs east and west through the southern half of the state; and Interstate 29, running north and south in the eastern portion of the state. The I-29 corridor features generally higher rates of population and economic growth than areas in eastern South Dakota further from the interstate. Also in the state are the shorter Interstates 190, a spur into central Rapid City, and 229, a loop around southern and eastern Sioux Falls. Several major U.S. highways pass through the state. U.S. routes 12, 14, 16, 18 and 212 travel east and west, while U.S. routes 81, 83, 85 and 281 run north and south. South Dakota and Montana are the only states sharing a land border that is not traversed by a paved road. South Dakota contains two National Scenic Byways. The Peter Norbeck National Scenic Byway is in the Black