This six-day trek begins with a gentle mile-long descent from Hellroaring Creek trailhead to the Yellowstone River. Cross the suspension bridge and join the Buffalo Plateau Trail at mile 1.5; head northeast to begin climbing up the wind-scoured plateau. Keep an eye out at mile two—the Buffalo Plateau Trail becomes faint and bears right at the fork with the Coyote Creek Trail. Cross into Montana on a 2,300-foot climb over 5.4 miles to a three-way intersection. Turn left and switchback another mile uphill to a natural spring and your first campsite (labeled 2B1).

In the morning, hike 2.1 off-trail miles, heading northwest through open meadows. Sweep east around an unnamed 8,716-foot peak to hit the Poacher’s Trail, just outside the park boundary. The trail doglegs west, plummeting a quick 900 feet to Coyote Creek. The next 2.7 miles follow the drainage north, round Bull Mountain (8,272 feet), and descend to Hellroaring Creek. Cross the bridge and go .7 mile to the Hellroaring Patrol Cabin. Camp here, in a vast creekside meadow where the author saw a black bear and cub.

On the third day, the route is flat and fast, hugging the river as it re-enters the park (do lunch at an unnamed creek .4 mile south of the posted boundary line). Finish this seven-mile day at the campsite marked 2H7 next to Hellroaring Creek. This is grizzly territory, so be extra cautious and pack all smelly items in a bear canister.

Day four’s route crosses high meadows--with a good chance to see elk--then joins the Yellowstone River. The next 4.6 miles flank the river, where there are plenty of shady waterfront rest stops to cool down.

Spend nights four and five downriver at Crevice Lake (1Y1) (11) and use the layover to dayhike the Black Canyon of the Yellowstone. Lunch and swim at a 100-yard-long, black-sand beach located 3.2 miles from Crevice Lake.

On the final day, double back upriver to the Blacktail Deer Creek Trail and hike the final 4.6-mile leg, climbing 1,000 feet from the Yellowstone River to the trailhead on Grand Loop Road.

WHEN TO GO: Relatively low elevations make this hike best from late April through late June (great for wildflowers) and early fall. Avoid the summer's heat.

PERMITS: Reserve in advance ($20 per trip) by mail beginning April 1. Some permits are also assigned on a first come basis, 48 hours prior to departure.

MORE INFO: Yellowstone National Park, (307) 344-2160; nps.gov/yell

--mapped by Michael Behar