About This Trip
The Grand Loop Road is the backbone of Yellowstone National Park, a figure-eight circuit covering 142 miles through the most geologically active landscape on the continent. The road visits every major thermal area, canyon, lake, and wildlife corridor in the park and can be driven in a day — but a minimum of two is strongly recommended to do justice to what is here.
Old Faithful anchors the Upper Geyser Basin, the densest concentration of geysers on Earth. The geyser erupts roughly every 90 minutes with remarkable consistency, shooting 3,700 to 8,400 gallons of water up to 185 feet. The surrounding boardwalk system passes dozens of other geysers, hot springs, and fumaroles — plan at least two to three hours here, especially with children.
The Grand Prismatic Spring, the largest hot spring in the United States and the third largest in the world, is a short detour from the main loop. The rainbow of colors — deep blue center, green and yellow rings, orange and red bacterial mats at the edges — is best seen from the overlook trail above, not from the boardwalk level.
The Lamar Valley in the northeast is Yellowstone's premier wildlife corridor. Bison herds in the thousands are common, and Lamar Valley is one of the few places in the lower 48 states with a reasonably reliable chance of seeing wolves. Pull into any of the road-side turnouts and scan the valley slopes with binoculars.
Best time to drive: June through September. The park roads are fully open from late April to early November; some sections close earlier. Summer weekends bring heavy traffic — entering before 8am makes a significant difference.
Stops
Old Faithful & Upper Geyser Basin
The world's most famous geyser erupts every 60 to 110 minutes and is visible from a large amphitheater that accommodates thousands of visitors. Allow at least 2 hours to walk the geyser basin boardwalk beyond Old Faithful — Beehive Geyser, Castle Geyser, and Morning Glory Pool are highlights. The Old Faithful Inn (1904) is the largest log hotel in the world and worth a walk through the lobby.
Grand Prismatic Spring
The largest hot spring in the United States — 370 feet across and over 121 feet deep. The iconic rainbow of colors comes from heat-adapted bacteria that form colored mats at different temperatures around the edges. The overlook trail (1.6 miles round trip) above the spring is the only place to see the full circular pattern; the boardwalk view from ground level is obscured by steam.
Grand Canyon of the Yellowstone
A 20-mile canyon up to 1,200 feet deep carved through yellow and orange rhyolite by the Yellowstone River. The Lower Falls, at 308 feet, are twice the height of Niagara Falls. Artist Point on the south rim offers the classic view down the canyon with the falls in the background — one of the most photographed spots in the American West.
Mammoth Hot Springs
A cascading series of travertine terraces built by hot spring water depositing calcium carbonate as it flows to the surface. The terraces change constantly as the springs shift — formations active five years ago may now be dry and gray. The Mammoth area also has the park's most reliable elk viewing; a resident herd grazes on the park headquarters lawn.
Lamar Valley
Yellowstone's 'Serengeti of North America' — a broad, glacially-carved valley where bison herds number in the thousands and wolves are regularly visible from roadside pull-offs. Early morning (before 8am) and dusk offer the best wildlife activity. Keep binoculars handy and pull fully off the road when stopping — traffic backups form quickly around any animal sighting.