The Moose River is a mountain waterway which consists of three branches: the North Branch, the Middle Branch and the South Branch. The outlet of Big Moose Lake forms the North Branch in northern Herkimer County. The Middle Branch originates at the Fulton Chain Lakes in Old Forge. And the Southern Branch has its headwaters in Little Moose Lake in Hamilton County. It flows generally westwardly through Herkimer County into Lewis County, reaching its confluence with the Black River in Lyons Falls.
Owing to its high gradient as it drops out of the mountains, The Moose is a favorite destination for whitewater rafters, kayakers and canoeists. There are three whitewater sections below McKeever with increasing degrees of difficulty. The Middle Moose is a Class II-III section of river from the gaging station in McKeever to Rock Island. The Lower is a Class III-V section from Rock Island to just above Fowlersville Falls, which is run commercially in early spring and includes drops such as Tannery, Froth Hole, Mixmaster and Miller's Falls. The Bottom Moose is a Class V+ section from Fowlersville on. In October of each year, hundreds of whitewater paddlers descend on the Moose from all parts of the US and eastern Canada. The Bottom Moose (see below), in particular, is a favorite run for paddlers who enjoy Class-V whitewater. This run has several waterfalls, ranging from straightforward and easy to difficult and dangerous.
Also because of its high gradient, there are several hydropower projects along the Moose's course.
The South Branch is a small stream as it emerges from Little Moose Lake, flowing around the base of Little Moose and Manbury Mountain. As it passes through the valley, it picks up another stream, Silver Run, and continues on over the rocks. Another five miles or so, and it passes under the newer concrete bridge on the main road in the Plains. Only another few hundred yards, and Otter Brook comes in from the left. Now the Moose, mostly flatwater, tumbles over a couple of short rapids/rifts and then forms a two-mile long stillwater before it arrives at an old log dam. This dam runs almost all the way across the river, and usually one can take a canoe over it with not much problem. Immediately after the dam, the river is all rapids, shallow most of the year, good for wading while you fish, but turbulent in the spring snow-melt or when a hard rain falls. These rapids continue on and off until, maybe a mile downstream, the Indian River joins in from the left. Then another mile of complete straight stillwater, most of it below a mountain cliff on your right, and the Moose rolls over Rock Dam, a huge nearly flat rock that almost completely dams the river. At this point, from your right, the Red River enters the Moose, and also flows over the same dam. This is only yards from the Herkimer/Hamilton County line, and a trail just below the dam, on the right bank, will take you up to the dirt road, maybe a mile and a half away. Now another mile or more of good rapids, and the North Branch of the Moose enters the Adirondack League Club's private property, as it leaves the Plains behind.
On June 15, 1991 five paddlers descended the South Branch of the Moose River from its source and into the private, posted property of the Adirondack League Club. The reason for the journey was to test the laws regarding the rights of the public to paddle on water that flows over private property. The League Club was given advance notice of the trip, and the trip was video taped by both groups as evidence. As expected the League Club promptly sued the paddlers, and the Sierra Club (who had organized the trip), for five million dollars.