More than 20 iron ore mines operated around the city of Crosby before going out of business in the 1960s, leaving behind 200-foot-high debris piles and 15 pits as deep as 525 feet. Eventually, forests returned to the land and water filled in the pits. In 1993, the Minnesota Department of Natural Resources turned roughly 5,000 acres of the former mining site near Brainerd into the Cuyuna Country State Recreation Area. Mountain bikers salivated over the landscape's potential and worked with the DNR to create winding, undulating singletrack trails in the area. The move rejuvenated the small town of Crosby, which today boasts bike shops, a brewery, a pizza joint, and other businesses that cater to the more than 28,000 bikers who visit Cuyuna each year.

Most two-wheeled fanatics come during the summer, leaving winter as a prime time to experience the trails without the crowds. It helps when temps drop to 13 below, as they did the December weekend when I visited with my friend Isaac. We rented fat tire bikes at Crosby's Red Raven Bicycle Cafe, where employees told us which trails were groomed and ready.

We set out on Saturday morning for beginner singletrack trails in a section called the Yawkey Unit. Isaac took off in the lead. Two deer darted up a hill as he entered the woods. His orange Salsa Mukluk bike stood out against the monochromatic backdrop of snow and leafless trees. Riding felt like floating, except when we wiped out into pillows of snow. On Sunday, we biked the Cuyuna Lakes State Trail to the Galloping Goose singletrack trail in the Mahnomen Unit. We looked out across frozen lakes. In front of me, I could see the steam from Isaac's breath. Near the end of our two-hour ride, Isaac looked at his watch to check our progress. It had stopped tracking data early, but he announced the readout anyway. "Three-point-six miles per hour. Total calories 290." The incomplete numbers were enough justification for me to reply, "That sounds like a good excuse for a sandwich at Red Raven."

Know Before You Go
• The Cuyuna area offers roughly 40 miles of groomed trails. Ratings vary from easy to very difficult. There are about 25 miles of groomed singletrack, 8 miles of doubletrack, and 7 miles of quad track.
• Only groomed trails that have been allowed to harden should be ridden, and only on bikes that have fat tires 3.7 inches across or wider. Bikers can pop into Red Raven Bicycle Cafe to see which trails are ready. If the trails aren't ready, snowshoeing and ice fishing are other outdoor options.
• There are plenty of places to stay. The Crosby Lofts offer lodging on Main Street with a room for storing bikes. True North Basecamp offers cabins with Wi-Fi steps from the trails. The DNR rents out three yurts with free firewood on the west side of Yawkey Mine Lake.

Fast Facts
• The International Mountain Bicycling Association has named the Cuyuna trails a Silver Level Ride Center, one of only 15 such places in the world.
• The designation is based on Cuyuna's high-quality trails for all skill levels, as well as the area's bike-friendly amenities and culture.
• Volunteers groom the singletrack trails. Roughly a dozen people prep trails with machines. Many more pack them down with snowshoes.
• The Minnesota DNR and the Cuyuna Lakes Mountain Bike Crew are working to expand the trails to more than 70 miles in the coming years.