Grant Brook is named after Samuel Grant, one of the first settlers of Lyme, who built a sawmill on the brook in 1764. The brook provides habitats for beavers, otters, and birds. 

The mouth of Grant Brook where it enters the Connecticut River is located north of Wilder Wildlife Management Area on River Road. There are ponds on both sides of River Road where the road crosses the brook.

Grant Brook falls 2,500 feet from its source on Smarts Mountain, through the villages of Lyme Center and Lyme; delivering run-off gathered from its 10 square mile watershed to the Connecticut River. The Grant Brook corridor is a rich riparian plant and animal habitat, of historical interest, and with excellent recreational possibilities. Several trails follow the last stretch of the brook, skirting along rock walls and pastures with wonderful views of surrounding hills; passing through beaver meadows, mixed hardwood and softwood forests, and open fields. 

The Upper Valley Land Trust website has descriptions and maps of hikes at Grant Brook.