The Mad River is a tributary

Tributary

A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...

 to the Winooski River

Winooski River

The Winooski River is a tributary of Lake Champlain, approximately long, in northern Vermont in the United States. Although not Vermont's longest river, it is one of the state's most significant, forming a major valley way from Lake Champlain through the Green Mountains towards the Connecticut...

 in Vermont

Vermont

Vermont is a state in the New England region of the northeastern United States of America. The state ranks 43rd in land area, , and 45th in total area. Its population according to the 2010 census, 630,337, is the second smallest in the country, larger only than Wyoming. It is the only New England...

. It has its headwaters in Granville Gulf, then flows north through the towns of Warren

Warren, Vermont

Warren is a town in Washington County, Vermont, United States. The population was 1,681 at the 2000 census. The center of population of Vermont is located in Warren. It is set between the two ranges of the Green Mountains, with approximately 25% of the town under Green Mountain National Forest...

, Waitsfield

Waitsfield, Vermont

Waitsfield is a town in Washington County, Vermont, United States. The population was 1,659 at the 2000 census. It was created by Vermont charter on February 25, 1782...

, and Moretown

Moretown, Vermont

Moretown is a town in Washington County, Vermont, United States. The population was 1,653 at the 2000 census.-Geography:According to the United States Census Bureau, the town has a total area of 40.2 square miles , of which 40.1 square miles is land and 0.1 square mile is...

 before entering the Winooski River just downstream from Middlesex

Middlesex, Vermont

Middlesex is a town in Washington County, Vermont, United States. The population was 1,729 at the 2000 census.-Geography:According to the United States Census Bureau, the town has a total area of 39.9 square miles , of which, 39.7 square miles of it is land and 0.2 square miles of...

. Other towns within the Mad River watershed are the entire Town of Fayston

Fayston, Vermont

Fayston is a town in Washington County, Vermont, United States. The population was 1,141 at the 2000 census.-History:The town was chartered in 1788 and sold to a speculator. The town was organized in 1805. This town has produced many greats such as Sir Samuel Luke Brown...

 and a portion of the Town of Duxbury. Relative to other rivers in the state, the Mad River is fairly rocky and clear, making it a popular for swimming. In the summer of 2008, didymo, or Rock Snot, was found in the upper portions of the river.

The Mad River Valley is a popular region with tourists due to its picturesque scenery and two ski areas, Mad River Glen

Mad River Glen

Mad River Glen is a ski area in Fayston, Vermont. Its terrain has been ranked by SKI magazine as the most challenging on the east coast of the United States. Located within the Green Mountain range, it sits in the Mad River Valley, close to the larger Sugarbush Resort...

 and Sugarbush Resort

Sugarbush Resort

Sugarbush Resort is a ski resort located in the Mad River Valley in Warren, Vermont. It is one of the largest ski resorts in New England. The resort encompasses more than 4000 acres total, 578 acres skiable, 53 miles of trails, and 16 ski lifts...

. Since 1990, the Friends of the Mad River - a non-profit formed to preserve and protect the recreational, ecological and aesthetic resources of the Mad River - has been engaged in citizen-based water quality monitoring, river restoration, land conservation, and public education and outreach on behalf of the Mad River watershed.