Colorado Just Threw A Week-Long Party To Celebrate The Nation's Most Difficult Bike Race

This was a happy day for U.S. cycling fans. About one million of them gathered on the roads along various stages of the race course to cheer on all the racers. (Jump straight to the pictures.)

Colorado, home to 53 mountains over 14,000 feet, is a place filled with fanatical cyclists. Many Colorado residents own at least three bikes: a road bike, a mountain bike and a "townie" with a big comfy seat used to commute, run errands.

The USA Pro Challenge is helping the country build a reputation for world-class, difficult stage races. Now in its third year, 128 riders from 31 countries on seven teams participated in the 2013 race, including 2013 Tour de France winner, British cyclist Chris Froome of Sky Procycling. But Froome didn't finish this race. He dropped out because of asthma.

This race course would give just about anyone an asthma attack. It covers countless hills in 600 miles in seven days across Colorado, including a ride up the highest mountain pass in any professional cycling race, Independence Pass, at 12,000 feet. The time trials, where racers ride 10 miles as fast as they can, are held on Vail Pass, at 10,000 feet.

The fans are insane, too. Every peak is a dance party. Like the Tour de France, people line the streets, many in costume, and crowd the cyclists as they pass by.