As the hub of the Rocky Mountain states, Colorado maintains extensive road and rail systems.
Because of its difficult mountain terrain, Colorado was bypassed by the first transcontinental railroads. In 1870, however, the Denver Pacific built a line from Denver to the Union Pacific's cross-country route at Cheyenne, Wyoming. Several intrastate lines were built during the 1870s, connecting Denver with the mining towns. In particular, the Denver and Rio Grande built many narrow-gauge lines through the mountains. Denver finally became part of a main transcontinental line in 1934. As of 2000, there were 3,515 rail mi (5,656 km) of track in the state, utilized by 12 railroads. This included two Class I railroads (which by definition carry more than $250 million a year in freight revenue). AMTRAK trains in Colorado had an annual ridership of nearly 250,000 persons in the mid-1990s.
Colorado has an extensive network of roads, including 29 mountain passes. As of 2000 there were 85,409 mi (137,452 km) of roadway in Colorado: 70,946 mi (114,176 km) classified as rural and 14,463 mi (23,275 km) as urban. The major state roads are Interstate 70, US 40, and US 50 crossing the state from east to west, and Interstate 25 running north–south along the Front Range of the Rocky Mountains between Raton Pass and Cheyenne, Wyoming. Interstate 76 connects Denver on a northeasterly diagonal with Nebraska's I-80 to Omaha.
Of the 3,724,309 motor vehicles registered in 2000, 1,920,757 were automobiles; 1,699,469 were trucks; and 5,786 were buses. There were 3,107,258 licensed drivers that year.
A total of 91 public-use airfields served the state in 2002. Denver International Airport (DIA) replaced the former Stapleton International Airport in 1994 as the state's largest and busiest. In 2000, DIA handled 18,382,940 enplanements. In 2003, Centennial Airport ranked as the 2nd-busiest general aviation airport in the nation and one of the 25 busiest airports of any kind.