Mountain biking is a fast-growing sport. Some folks take it easy, pedaling their way to wild country on smooth, easy-grade paths; others are looking for a fast ride down on bumpy, steep trails. Bring your own bike or rent from a local bike shop that will likely assist you in finding the best spots to ride. Bicycling on roads is also popular, but there are limitations: While automobile traffic on many roads is light, there isn't much room, because most of the roads have skimpy shoulders -- Yellowstone roads are among the worst. Nor are drivers in this region terribly respectful of bicyclists. So be watchful, research your routes so you can keep to the wider roads, and always wear that helmet.

Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.