Mammoth Hot Springs lies at an elevation of 6,239 feet near the northern border of Yellowstone , just five miles from the town of Gardiner, Montana. Here you’ll find park headquarters, a variety of other facilities, and delightfully colorful hot springs.
The Mammoth area is an important wintering spot for elk, pronghorn antelope, deer, and bison. During the fall, at least one bull elk and his harem can be seen wandering across the green lawns, while lesser males bugle challenges from behind the buildings or over the hill. The bugling may even keep you awake at night if you’re staying in the Mammoth Hotel.
Mammoth Hot Springs consists of a series of multihued terraces down which hot, mineral-laden water trickles. This water originates as snow and rain that falls on the surrounding country, although some is believed to come from the Norris area , 20 miles to the south. As it passes through the earth, the water comes into contact with volcanic magma containing massive amounts of carbon dioxide, creating carbonic acid.
The now-acidic water passes through and dissolves the region’s sedimentary limestone, and the calcium carbonate remains in solution until it reaches the surface at Mammoth. Once at the surface, the carbon dioxide begins to escape into the atmosphere, reducing the acidity and causing the lime to precipitate out, forming the travertine terraces that are so prominent here. As the water flows over small obstructions, more carbon dioxide is released, causing accumulations that eventually grow into the lips that surround the terrace pools.
The rate of accumulation of travertine (calcium carbonate) is astounding: more than two tons a day at Mammoth Hot Springs. Some terraces grow by eight inches per year. The first explorers were fascinated by these terraces; mountain man Jim Bridger noted that they made for delightful baths. A later operation—long since ended—coated knickknacks by dipping them in the hot springs!
The springs are constantly changing as underground passages are blocked by limestone deposits, forcing the water in new directions. As a result, old dried-out terraces stand on all sides, while new ones grow each day. Areas that were active just a few years ago may now be simply gray masses of crumbling travertine rock, and new areas may appear and spread in a matter of days.
Mammoth is guaranteed to be different every time you visit. One of the most interesting aspects of the hot springs here is the variety of colors, a result of the many different species of algae and bacteria that live in the water. Various factors, including temperature and acidity, affect the survival of different species; bright yellow algae live in the hottest areas, whereas cooler waters are colored orange and brown by other algae.
Mammoth Hot Springs covers a steep hillside and consists of a series of colorful springs in various stages of accretion or decay. The area is accessible by road from below or above (Upper Terrace Drive), and a boardwalk staircase connects the two levels. At the bottom of Mammoth Hot Springs and off to the right is a 37-foot-tall mass of travertine known as Liberty Cap for its faint similarity to the caps worn in the French Revolution. The spring that created this formation no longer flows. (You may well think Liberty Cap shows a more striking similarity to something else a bit more—shall we say—masculine.)
The springs at Mammoth change continuously, and every visit brings something new. For details on currently active areas, pick up the Park Service’s informative brochure ($0.50) from the box at the parking area. The most interesting areas in the last few years have been Palate Spring near the base and the very active Canary Spring in the vicinity of the overlook. Along Upper Terrace Drive, both Angel Terrace and Orange Spring Mound have started flowing again after decades of inactivity.
All of the water flowing out of Mammoth terraces quickly disappears into underground caverns. In front of the Mammoth Hotel are two sinkholes from which steam often rises. Caverns above the terraces were once open to the public but were closed when it became apparent that they contained poisonous gases. Dead birds are sometimes found around one of the small pools in this area, appropriately named Poison Spring.
Mammoth contains several historic structures built during the army’s tenure at Fort Yellowstone. The most distinctive are the six buildings (all in a row) constructed between 1891 and 1909 as quarters for the officers and captains. Most of the grunt soldiers lived just behind here in barracks, one of which is now the park administration building. The U.S. Engineers Department was housed in an odd stone building with obvious Asian influences; it’s right across from the visitor center. The visitor center has an informative pamphlet ($0.50) that describes the Fort Yellowstone Historic District in detail. Displays around the grounds provide additional details.
Although one wing survives from a hotel built in 1911, most of the Mammoth Hot Springs Hotel was constructed in 1937. Step inside to view a large map of the United States built from 15 different types of wood. Mammoth also features a Yellowstone General Store, post office, gas station, restaurant, fast-food eatery, and medical clinic. Mammoth Campground is a short distance down the road. Just up the hill—less than a mile from the hotel—is the Mammoth corral, where horseback rides are offered. Also here is a small cemetery populated mostly by infants and a few civilians who died here in the early 1900s.
Named for Horace Albright—Yellowstone’s first National Park Service superintendent—the Albright Visitor Center (daily 8 a.m.-7 p.m. late May-Sept., 9 a.m.-5 p.m. the rest of the year) is housed in the army’s old bachelor officers’ quarters. Spread over two floors are exhibits on park wildlife and history, but the real treats are the works of two artists who helped bring Yellowstone’s magnificent scenery to public attention. Twenty-three of painter Thomas Moran’s famous Yellowstone watercolors line the walls (though they’re hard to see in the dim lighting), and his studio has been re-created in one corner. Equally impressive are 26 classic photographs—including one of Thomas Moran at Mammoth Hot Springs—taken by William H. Jackson during the 1871 Hayden Survey. The paintings and photos are must-sees for anyone with an artistic bent. The center also has an information desk, videos about the park and Moran every half-hour, and racks of books. Check at the information desk for schedules of wildlife talks and frequent ranger-led walks to surrounding sights in the summer.
The main park road north from Mammoth Hot Springs follows the Gardner River, dropping nearly 1,000 feet in elevation before reaching the town of Gardiner, Montana. (Both the river and the misspelled town are named for Johnson Gardner, a ruthless trapper from the 1820s.) The river is a favorite of fly-fishing enthusiasts. A turnout near the Wyoming-Montana border notes the “boiling river” section of the Gardner; it’s always worth a stop, and the 0.5-mile hike has a big reward at the end. Bring your swimsuit! Sometimes during the winter you can spot bighorn sheep on the mountain slopes just north of the river as you head down to Gardiner.
The “back way” to Gardiner is the Old Gardiner Road, a five-mile gravel road (great for mountain bikes, but not for RVs or trailers) that starts behind Mammoth Hot Springs Hotel. Traffic is downhill only, so you’ll need to take the main road for your return into the park; mountain bikes can go in both directions. This is one of the best places to spot pronghorn antelope in the park, and it also provides a fine escape from the crowds at Mammoth.
The 18-mile drive from Mammoth to Tower Junction takes visitors through some of the driest and most open country in Yellowstone. Two waterfalls provide stopping places along the way. Beautiful Undine Falls is a 60-foot-high double fall immediately north of the road. Just up the road is a gentle 0.5-mile path to the base of Wraith Falls, where Lupine Creek cascades 90 feet. Look for ducks and trumpeter swans in Blacktail Pond, a couple of miles farther east.
Blacktail Plateau Drive, approximately nine miles east of Mammoth, turns off from the main road. The rough seven-mile dirt road is a one-way route that loosely follows the Bannock Trail, a path used by the Bannock tribe on their way to buffalo-hunting grounds east of here. Their travois trails are still visible. The Bannocks used this route from 1838 to 1878, but it was probably used for hundreds or thousands of years by various tribes crossing the high plateau. Much of Blacktail Plateau Drive is through open sagebrush, grass, and aspen country, where you’re likely to see deer and pronghorn antelope. The trees are very pretty in the fall. On the east end, the road drops back into a forest burned by a severe crown fire in 1988 but now containing young aspen and lodgepole pines and abundant summertime flowers.
A two-thirds-mile boardwalk, Forces of the Northern Range Self-Guiding Trail, is six miles east of Mammoth Hot Springs. Half a mile beyond where Blacktail Plateau Drive rejoins the main road is the turnoff to the petrified tree. The 20-foot-tall stump of an ancient redwood tree (50 million years old) stands behind iron bars; a second petrified tree that used to stand nearby was stolen piece by piece through the years by thoughtless tourists. The Tower Ranger Station, originally occupied by the U.S. Army, is just before Tower Junction where the road splits, leading to either Northeast Entrance Road or Canyon.