[3] Although the Grand Central and Kruzgamepa (or Pilgrim) rivers form one stream, their names differ, and their physical features vary.

The drainage area of this stream is almost surrounded by ridges of the Sawtooth Range (Kigluaik Mountains), having elevations of 1,500 to 4,000 feet (460 to 1,220 m).

The river is formed near the foot of Mount Osborn, at an elevation of about 700 feet (210 m), by the junction of North and West forks, and flows in a southerly direction into Salmon Lake.

From the forks to Salmon Lake, the river has a fall of about 300 feet (91 m), and at high stages, spreads over a wide gravel bed.

These tributary streams, with the exception of Nugget Creek, drain short, steep-sided gulches.