Saved from damming by local conservationists, the Buffalo River was declared the country's first national river in 1972. Ken Smith, 79, has spent the past 25 years forging a trail that will ultimately extend from the Buffalo's source in the Boston Mountains to its convergence with the White River, 135 miles west. This summer, he recommends "float hiking" the 24-mile segment from Ponca to Pruitt Landing: Hike upstream through blue hills of hickory, peer over 500-foot limestone cliffs, and then spend a couple of days kayaking back downriver past plunging waterfalls.

Getting there: Fly into the Boone County Airport from either Kansas City or Memphis. From there, a 35-minute drive on A.R. 43 will bring you to Ponca, where the Buffalo Outdoor Center has cabins to rent from $129 to $300 and kayaks for $58 per day.