A century-old lightkeeper’s house on Isle au Haut in Maine that’s listed on the National Register of Historic Places has been sold, and the new owner plans to reopen it as an inn. Marshall Chapman, a college professor and longtime island summer resident, purchased the property recently from longtime owners Jeffrey and Judith Burke. The Knowles Company, a Northeast Harbor-based real estate firm that handled the sale, says the property had been listed for $1.9 million and sold for $1.5 million. The 2-acre oceanfront property includes a four-bedroom, turn-of-the-century lightkeeper’s house, a guest house, several cottages, a boathouse and a deep water dock. As the Keeper’s House inn, it became a popular destination for people from around the world and was featured in newspapers, magazines and television.