To make the most of a Yellowstone day trip, concentrate your efforts inside the caldera to see the most geothermal activity. The South Grand Loop will circle mostly within the caldera rim.
From West Yellowstone, drive the Madison River Valley toward National Park Mountain. This wildlife corridor harbors bison and elk. Look for them in the meadows, but be ready to brake as they can be in the road.
At Madison Junction, turn north to follow the Gibbon River, stopping at Gibbon Falls. You’ll climb out of the supervolcano caldera en route to Norris Junction, where a right turn continues following the Gibbon River. Within a mile, you’ll drop back into the caldera to continue toward Canyon Junction.
At Canyon Junction, stop at the Canyon Visitor Education Center to learn about the volcano’s workings. From there, drive Grand Loop Road south to South Rim Drive to reach Artist Point for views of Lower Yellowstone Falls. Then, if you’ve got gumption, stop at Uncle Tom’s Trail to hike the stairway down to stand level with the falls to hear its roaring thunder.
Continue south through Hayden Valley watching for wildlife as you follow the Yellowstone River upstream to Yellowstone Lake, the largest freshwater lake above 7,000 feet in North America. En route, you’ll see increasing geothermal activity with fumaroles and mud pots. Stop at the historic Lake Yellowstone Hotel to dine for lunch.
After lunch, follow Yellowstone Lake south to Grant Junction to head west to Old Faithful by crossing the Continental Divide to drop into the Firehole River Valley. Tour the boardwalk loop around Geyser Hill, but check the signs first, so you can catch Old Faithful Geyser erupting. Stop in the Old Faithful Inn to tour the historic log lobby. Then, follow the Firehole River north to Midway Geyser Basin to walk the boardwalk to see Grand Prismatic Spring. Watch for wildlife as you descend the valley past steam vents to return to Madison Junction and back to West Yellowstone.
Excerpted from the Seventh Edition of Moon Yellowstone & Grand Teton.