Just a few miles south of the Grand Canyon , the country abruptly opens into beautiful Hayden Valley, named for Ferdinand V. Hayden, leader of the 1871 expedition into Yellowstone. Reaching eight miles across, this relatively level part of the park was once occupied by an arm of Yellowstone Lake .
The sediments left behind by the lake, along with glacial till, do not hold sufficient water to support trees. As a result, the area is occupied primarily by grasses, forbs, and sage. This is one of the best areas in the park to see wildlife, especially bison and elk.
The Yellowstone River wanders across Hayden Valley, and streams enter from various sides. These waterways are excellent places to look for Canada geese, trumpeter swans, pelicans, and many kinds of ducks. Wolves are also frequently sighted; just look for the line of cars and the crowds with binoculars and spotting scopes.
Although they are less common, grizzly bears can sometimes be found feeding at the eastern end of the valley. Because of the bears, hikers need to be especially cautious when tramping through the grasses and shrubs, where it is easy to surprise a bear or to be likewise surprised.
On the north end of Hayden Valley, the road crosses Alum Creek, named for its highly alkaline water, which could make anything shrink. In the horse-and-buggy days, Yellowstone wags claimed that a man had forded the creek with a team of horses and a wagon but came out the other side with four Shetland ponies pulling a basket!
The park road climbs south out of Hayden Valley to pass one of the most interesting of Yellowstone’s many thermal basins. On the east side of the road, a turnout overlooks Sulphur Caldron, where a highly acidic pool is filled with sulfur-tinted waters and the air is filled with the odor of hydrogen-sulfide gas. Directly across the road is the Mud Volcano area, where a two-thirds-mile loop trail provides what could be a tour through a bad case of heartburn. Pick up a Park Service brochure ($0.50) from the box for descriptions of all the bizarre features here.
The area is in a constant state of flux as springs dry up or begin overflowing, killing trees in their path. Churning Caldron is a frothing pool where periodic jets send superheated water into the air. Just up the trail is one of the most interesting features, Black Dragons Caldron, where an explosive spring blasts constantly through a mass of boiling black mud. The wildest place at Mud Volcano is Dragon’s Mouth Spring, which the Park Service notes is named for “the rhythmic belching of steam and water shooting from the cavernous opening.” It’s easy to imagine the fires of hell not far below this spring. The waters are 170°F. During winter (and often in summer), the Mud Volcano area is a good place to see elk or bison.
The park road parallels the Yellowstone River south of Mud Volcano. At LeHardys Rapids, a boardwalk provides an overlook where early-summer visitors see blush-red spawning cutthroats. In late summer, this part of the Yellowstone River is a very popular fly-fishing spot—some call it the finest stream for cutthroat fishing in the world—and a good place to view ducks and swans. Earlier in the year, it’s open only to the bears that gorge on the cutthroats. By the way, the Yellowstone River, which begins at Yellowstone Lake , is the longest free-flowing (undammed) river in the Lower 48.