Waterville Valley is a New England town in Grafton County, New Hampshire, United States. The population was 508 at the 2020 census, up from 247 at the 2010 census. It is a resort town which attracts many visitors in the winter months with alpine skiing at Waterville Valley Resort and many miles of trails for cross-country skiing. During the summer, …Waterville Valley is a New England town in Grafton County, New Hampshire, United States. The population was 508 at the 2020 census, up from 247 at the 2010 census. It is a resort town which attracts many visitors in the winter months with alpine skiing at Waterville Valley Resort and many miles of trails for cross-country skiing. During the summer, attractions include a golf course, tennis courts, and a variety of hiking options. The Mad River flows through the town, providing great views all year round.