The mountain is in the heart of the High Peaks Wilderness Area in Adirondack Park. Like the surrounding Adirondack Mountains, Marcy was heavily affected by large glaciers during recent ice ages, which deposited boulders on the mountain slopes and carved valleys and depressions on the mountain. One such depression is today filled by Lake Tear of the Clouds, which is often cited as the highest source of the Hudson River. The majority of the mountain is covered by hardwood and spruce-fir forests, although the highest few hundred feet are above the tree line. The peak is dominated by rocky outcrops, lichens, and alpine plants.

Multiple approaches to the summit are available from the north and south, with the most popular route being the Van Hoevenberg Trail. The first recorded ascent of the mountain was made by a party led by Ebenezer Emmons on August 5, 1837, who named it after New York governor William L. Marcy. One of the mountain's most notable ascents was made in 1901, when Theodore Roosevelt climbed it with his family, and learned during his descent that William McKinley was dying and he was to become President of the United States.

During the Pleistocene Epoch, large glaciers formed across the Adirondack Mountains, carving new valleys and depositing erratic rocks across the mountains. The last glacial retreat of the Pleistocene occurred 12,000 years ago. Numerous cirques were left on the mountain slopes by water as it repeatedly froze and thawed, including a depression on the northeast slope known as the snowbowl, and another on the south slope which has now been filled by Lake Tear of the Clouds. The mountain, along with the surrounding Adirondack region, is currently rising at a rate of 2-3 millimeters per year.

Van Hoevenberg Trail

Hard

Must be in good physical condition, wear good hiking shoes/boots, and using trekking poles is highly recommended. Terrain conditions include steep inclines/declines, rock scrambling, uneven ground, very rooty and rocky trails.

Route type: Out and Back

Length: 15.8 miles