Alley Spring is the postcard of the Ozark National Scenic Riverways: a red three-story roller mill from 1894 standing over a turquoise spring pool that pushes out around 81 million gallons a day. The swimming is a few hundred yards downstream, where the spring branch joins the Jacks Fork and the river runs over a wide gravel bar below the campground. A short path from the campground loops leads to the bar, and on summer afternoons it is lined with chairs, coolers and kids in tubes. The Jacks Fork here is fed by the spring, so it runs clear and cold, around 57 degrees at the spring itself and warming a bit in the riffles; the deep hole against the bluff is the swimming spot, and the gravel shallows suit small children.

Alley Spring is six miles west of Eminence on MO 106, on the National Park Service side of the road. There is no entrance fee to the Riverways, and the day-use area, mill grounds and swimming are free. The campground charges a per-night fee through recreation.gov; it is open year-round, with the flush toilets and showers on from April 15 to October 15, an electric loop, paved pads, an amphitheater and ranger programs at the mill in summer. Weekends from Memorial Day to Labor Day book solid.

This is also a put-in and take-out on one of Missouri's most floated rivers. The Alley Spring to Eminence stretch is six to seven miles of easy Class I water with gravel bars, bluffs and a couple of small springs along the way, a half-day canoe or kayak trip that outfitters in Eminence run all summer with shuttles. Upstream, the Jacks Fork from Buck Hollow or Bay Creek down to Alley is the classic spring float, with the Jam Up Cave section when the water is up. The park service posts river levels and closes the river to floating in high water.

Around the mill, the Alley Overlook Trail climbs the bluff for a view down onto the spring, and the Chubb Hollow and Ozark Trail segments strike off into the oak woods for longer hikes. The mill itself is open for tours in season; it ground wheat and corn for the surrounding farms and ran the community's general store, school and post office until the 1920s. Come on a weekday morning in June if you want the spring pool and the swimming hole close to yourself; by Saturday noon the campground parking is full and the gravel bar is a party.