Underhill is within Vermont's 39,837-acre Mt. Mansfield State Forest. On the headwaters of the Brown's River, at about 2,000 feet elevation, the park lies on the west slope of 4,300 feet Mt. Mansfield, the state's highest peak. Just over the summit ridge is the Stowe ski area, one of North America's original ski resorts.

The elevation and corresponding exposure to harsh climatic conditions have resulted in some relatively unusual vegetation types along the mountain's summit ridge. The low, stunted-plants found in the alpine tundra near the summit, very rare in New England, are more typical of types found on broad expanses of Arctic tundra a thousand miles farther north. These plants are fragile (if you hike to the summit, please stay on marked trails.)

The park includes a log picnic shelter, built by the Civilian Conservation Corps or CCC, a nationwide public works program created during the great economic depression of the 1930’s to provide jobs and training for thousands of unemployed. Many state and national parks trace their origins to the CCC era.

In addition, the park contains a small campground, picnic grounds, and a group camping area.   The campground has a restroom facility with flush toilets and cold running water, but no showers.  Due to the park’s hillside nature, it is not suitable for RVs or trailers.  All campsites are walk-in.  This off-grid park uses solar power for office functions, and to operate the water system.