Book excerpt: These trips (nearly 40 of them) will lead the mountain biker to some of the most beautiful parts of Montana, Idaho, Wyoming, and South Dakota, and explain in detail how to explore them safely and responsibly, yet with all the thrills that mountain biking can produce. Follow routes that get you into the heart of backcountry within minutes of Missoula and Rapid City; find the low-traffic trails surrounding Glacier and Yellowstone National Parks (themselves off-limits to mountain bikes); discover the magnificent areas where no one goes The Big Hole Valley, the North Fork Flathead River.