Rattlesnake Island is a large island in Lake Winnipesaukee in the town of Alton, New Hampshire. It measures about two miles long with around five miles of shore land which is all privately owned. The interior of the island is conservation area. It is the highest (in elevation) island on Lake Winnipesaukee offering great views of the Broads and Sandwich Mountain Range to the north. The Rattlesnake Island Association is a great resource for those interested in unique island living on the “big lake”.