|Elevation||4,347 ft (1,325 m)|
|Prominence||640 ft (200 m)|
|Parent peak||Mount Skylight|
|Listing||Adirondack High Peaks 26th|
|Location||Keene / North Hudson, Essex County, New York|
|Marcy Group of the Great Range|
|Topo map||USGS Mount Marcy|
The south side of Allen Mountain drains into White Lily Brook, thence into the Boreas Ponds, the Boreas River, the Hudson River, and into New York Bay. The southwest side drains into Dudley Brook, thence into the Opalescent River, and the Hudson River. The northwest side drains into Allen Brook, thence into Skylight Brook, and Dudley Brook. The northeast side drains into Marcy Brook, thence into Stillwater Inlet, Upper Ausable Lake, and the Ausable River, which drains into Lake Champlain, and ultimately into Canada's Gulf of Saint Lawrence. The east side drains into Sand Brook, and thence into Stillwater Inlet.
Many experienced hikers in the area consider Allen Mountain to be the most difficult to climb of the 46 Adirondack High Peaks.