The North Mowich River's headwater tributaries drain North Mowich Glacier near an area of Mount Rainier called Division Rook. Shortly below the toe of the glacier, the river drops over a large wall, forming Moraine Falls, the first of two waterfalls on the river, both of which are very difficult to access and would take several days to reach on foot. Giant Falls, just as difficult to reach, is located a ways downstream of Moraine Falls. Ptarmigan Ridge separates the North Mowich River's headwaters from Spray Park, much of which is drained by other tributaries of the North Mowich River. Spray Creek rises in Spray Park, tumbles over Spray Falls, and collects a tributary called Grant Creek. Spray Creek then flows down from Spray Park and along the bottom of the steep slope called Eagle Cliff, after which it joins the river.