Falling over a sharp 101-foot drop, Rainbow Falls is an easy 2.5 mile walk from the trailhead at Devil's Postpile National Monument in Mammoth Lakes. The elevation gain is only 300 feet so it's a fairly easy hike to this natural wonder. Rainbow Falls is the highest water fall on the Middle Fork of the San Joaquin River. Plunging 101-feet down to the turbulent water below, the falls are aptly named for the many rainbows that appear in its mist throughout sunny summer days.
Visitors interested in a moderate day-hike can make a loop, embarking from the Ranger Station's trailhead to the Falls and returning via Shuttle Bus Stop 9, the Rainbow Falls Trailhead. The shuttle bus, which runs approximately every 20 or 30 minutes, can then return hikers to the Monument's Ranger Station from the Rainbow Falls trailhead.
This hike includes two fascinating geological features. First, you take a well marked trail 1/2 mile to Devil's Postpile, a baffling series of crystallized vertical columns of lava, caused by differing rates of cooling. After walking on top and around the Devil's Postpile, you'll continue on the well marked trail for 2 miles to Rainbow Falls which feeds into the powerful San Joaquin River, the largest river in Central California which travels over 365 miles to the Pacific Ocean near San Francisco Bay. The headwaters of the San Joaquin River start not far away at Thousand Island Lake at almost 10,000 feet (3,000 m) above sea level.
After relaxing near the falls, you will return on the same trail and head towards the Reds Meadow Resort for the shuttle bus back to Mammoth Mountain.
Permits are required for all overnight trips in wilderness areas. While Devils Postpile National Monument can issue permits through a special arrangement with the Inyo National Forest, it is best for visitors planning on a backpack trip in the area to contact the Inyo's Wilderness Permit office directly. The most current regulations and trail quotas can be found by visiting the Inyo National Forest's website or by phoning the Inyo's Wilderness Permit Office at (760) 873-2485.