 According to the United States Census Bureau, the town has a total area of 42.3 square miles (109.6 km2), of which 41.9 square miles (108.5 km2) is land and 0.4 square mile (1.1 km2) (0.97%) is water.It is drained by the Williams River, the Saxtons River, and several brooks that drain directly to the Connecticut River; the latter river is the eastern boundary of Rockingham.It is crossed by Interstate 91, U.S. Route 5, Vermont Route 103 and Vermont Route 121.