MINNEAPOLIS (AP) — Flooding in northern Minnesota is threatening a a group of historic buildings, including a renowned environmentalist’s retreat. The Minneapolis Star Tribune reports that flooding is threatening many properties in the Rainy River Basin. Rainy Lake just outside of International Falls is expected to rise another foot in the next few days and break a 1950 record. Resort, cabin and business owners across the region have been filling sandbags for days. One of the properties is environmentalist Ernest Oberholtzer’s retreat on Mallard Island. Oberholtzer lived on Mallard Island until 1957 and lobbied against a series of proposed dams in the northern watershed in the 1920s, an effort that helped establish the Boundary Waters Canoe Area Wilderness and Voyageurs National Park.