6. Missoula, Mont.
Number of bicycle commuters: 2,543
Bicycle commuters' share of overall population: 7.2%
A town with great bike infrastructure and a strong college presence can't help but encourage bicycle commuters.
University of Montana students make up nearly a quarter of Missoula's population and the university itself is the biggest employer in the city, which makes the city's bicycle commuter base heavily dependent on the student body. It has plenty of infrastructure to support it, though, with 25 miles worth of trails in town, another 140 miles of trails in adjacent national forests, a strong circle of bike shops, a handful of community biking organizations and a sustainable commuting group, Missoula in Motion, that calculates the mileage racked up by registered users via biking, balking, busing, telecommuting and other commuting alternatives.
What Missoula has working against it, however, are winters in which the average high temperature is below freezing in December and January and the average low temperature dips below freezing in October and doesn't unfreeze until April or May. That didn't stop the 44,700-member Adventure Cycling Association from setting up its headquarters in Missoula and plotting out U.S. bike routes, distributing maps and selling bike travel gear from its cozy Montana confines.