Grindstone island is the fourth largest island in the Thousand islands region. Forty percent of the island is protected by conservation easements through the Thousand Island Land Trust. Immerse yourself in nature, enjoying the many nature trails and points of interest. Make certain to visit the Grindstone Island winery to enjoy their many summer events. Grindstone Island is a few minutes of a boat ride to the historic and quaint village of Clayton, N.Y.