Since 2001, the nonprofit American Prairie Reserve has been working to restore the northern great plains to the pristine condition Lewis and Clark found them in more than 200 years ago. The resulting reserve, in northeast Montana, is now 305,000 acres. The aim is to reach 3.5 million by 2030, creating a U.S. Serengeti and the largest wildlife park in the lower 48, where herds of elk, mule deer, and bison thrive. But don’t wait to go. You can sleep under the stars now at the 11-site Buffalo Camp ($10), four miles north of the Charles M. Russell National Wildlife Refuge, and take a DIY mountain-biking safari on old ranch roads, passing grazing bison and scanning the skies for American kestrels, Sprague’s pipits, and Swainson’s hawks. Or paddle the Missouri River past pioneer homesteads and historic tepees to Kestrel Camp, a set of five luxurious yurts, each with AC, a hot shower, and a veranda for sundowners (from $4,800 for six days).