Phelps Mountain stands within the watershed of the West Branch of the Ausable River, which drains into Lake Champlain, thence into Canada's Richelieu River, the Saint Lawrence River, and into the Gulf of Saint Lawrence. The south side of Phelps Mtn. drains into Phelps Brook, thence into Marcy Brook, and the Ausable's West Branch. The northwest side of Phelps Mtn. drains into Pelkey Brook, thence into Marcy Brook. The northeast side of Phelps drains into Klondike Brook, thence into Marcy Brook.
Phelps is climbed regularly, and has a well marked trail. The trail is rocky and is very steep in some parts of the final approach to the summit. There are good views of Marcy, Colden, and Algonquin near the summit. There are also views of the ridge formed by Tabletop, Yard, and Big Slide. There is a partial view of The Great Range, and Giant can be seen in the distance.