Although it’s size today is scarcely a shadow of its former mass, Arapaho Glacier still retains the distinction of being Colorado’s largest glacier. It is only about a quarter-mile long, a half-mile wide, and 200 feet thick-tiny by world standards. Nevertheless, it really is a glacier and not just a snowfield. Geologists from the University of Colorado have confirmed that it is still moving, ever so slowly, so it is classified as a true glacier. Arapaho is also one of the state’s most easily accessible glaciers. It is situated only 3.5 miles from the Fourth of July Trailhead, and there is an excellent viewpoint high above its southern slopes in a shallow pass between Caribou Peak and South Arapaho Peak.

The glacier is almost due north of the trailhead, and to reach it you must climb up the northern side of the U-shaped valley. The valley is over 2,500 feet deep and looking up at your destination can be an intimidating experience, but the trail’s grade is fairly moderate, climbing only about 700 feet per mile.

Begin by walking west up the valley on the Arapaho Pass Trail. After 0.8 mile you will come to a junction where the trail to Diamond Lake branches off to the left. There are usually more hikers going to Diamond Lake than Arapaho Glacier, so you should notice a decrease in the number of people on the trail after passing this junction.

Another 1.0 mile beyond the Diamond Lake Junction will bring you to the next junction where you must turn right onto the Arapaho Glacier Trail. The elevation here is 11,250 feet, and there isn’t much left of the lush forest that originally shaded the trail-just an occasional grove of stunted spruce trees. Soon even they too will be gone as you cross into the alpine tundra above timberline. But before you continue stop to see the Fourth of July Mine on a small mound of tailings just north of the trail junction.

The Fourth of July Mine was first opened in 1875 after silver was discovered in the area. The amount of silver extracted from the claim proved disappointing, but that didn’t prevent its unscrupulous owners from thinking up other unsavory ways to make their investment pay off. When the silver had played out they managed to convince others that a huge deposit of copper lay under the mine, and millions of dollars were made selling worthless stock to the victims of their scheme. Today it has been over a hundred years since the claim was worked but there are still a few pieces of rusting equipment scattered about, including a large boiler and parts of a wench.

From the Fourth of July Mine the trail continues climbing to the east for another 1.7 miles before it reaches the Arapaho Glacier Overlook. This part of the trail is all above timberline, and the views looking down into the North Fork of Middle Boulder Creek are gorgeous. Diamond Lake lies below in a basin above the south side of the valley, and you can clearly see the trail below winding up to Arapaho Pass west of the Fourth of July Mine. At the turn of the century there was a wagon road up the east side of Arapaho Pass, but no trace of it remains now.

Finally, about an hour after leaving the Fourth of July Mine, the trail arrives at the glacier viewpoint in a saddle on the ridge east of South Arapaho Peak. The viewpoint offers a superb overview of the ice field; it is about 500 feet above the bottom of the glacier and 700 feet below the top of South Arapaho Peak. The ice flow has pushed up a small moraine in front of the glacier and a small frozen lake, or tarn, fed by the melting snow, lies behind the natural dam. When I saw the glacier in 2000 there was a large vertical cleavage a few hundred feet behind the tarn where a section of the snow pack had broken away and slid downward. This fault afforded an opportunity to look at a cross section of the glacier and estimate the thickness of the milky blue ice: the vertical height of the cleavage appeared to be about 150 feet.

Seeing the glacier from the overlook point gives one a compelling urge scramble down for a closer look, but unfortunately that is now illegal. In 1927 the city of Boulder acquired the Arapaho Glacier as part of a 3,685 acre land purchase from the federal government for the purpose of protecting the city's water supply. Boulder now has the distinction of being the only city in the United States that owns a glacier. It also owns several pristine lakes further down the valley that are strictly off limits to the public.

Many hikers climb to the summit of South Arapaho Peak after reaching the glacier overlook. The peak rises 700 feet above the trail to an elevation of 13, 397 feet. Although the climb is a very tiring scramble up an incline of about 30 degrees, it is not particularly difficult, and most climbers reach the top in about 45 minutes. It is also possible to traverse along the ridge from South Arapaho Peak to North Arapaho Peak, which at 13,502 feet is the highest mountain in the Indian Peaks Wilderness Area. The traverse to North Arapaho Peak is a more difficult scramble, however, than the climb up South Arapaho and takes at least another hour each way.

Soon after leaving the glacier overlook the trail passes the highest point on this hike and then slowly proceeds downhill along the ridge separating the North Boulder Creek drainage from the North Fork of Middle Boulder Creek. The views north of the ridge are very scenic; the valley below is decorated by a string of a half-dozen lakes that are fed by the Arapaho Glacier. Unfortunately these lakes are also owned by the city of Boulder, and hikers are not allowed to enter the valley. About 3.3 miles after leaving Arapaho Glacier, just before the trail again reaches timberline, you will begin to see a series of signs warning you not to venture north of the trail.

Finally, two miles before you reach the trailhead the trail again drops into a forest of spruce, subalpine fir and lodgepole pine as it descends to the Rainbow Lakes area, and soon it begins to follow a wire fence that Boulder claims to be the boundary line of its property. You should arrive at the Rainbow Lakes Campground about three hours after leaving the glacier overlook.