Following Adventure Cycling's epic Great Divide Mountain Bike Route, the Tour Divide travels 2,745 miles of mostly unpaved road and trail, crisscrossing the Continental Divide 29 times. Truly a grassroots event, there is no entry fee, prize money, and little to no media coverage of the ride. In classic touring tradition, riders in the race are entirely self-supported, carrying everything they need - food, water, shelter, tools - on their bikes and backs, making the Tour Divide not only the world's longest mountain bike race, but the most challenging cycling race in existence.

What follows are a series of pictures taken by Aaron Teasdale on the first day of the 2009 race.