Because the timber dams in the Mississippi headwaters had started to rot, Major Lockwood began to replace them with steel and concrete structures. He established flowage rights in anticipation of the growing recreational development in northern Minnesota. Because land was becoming more expensive, the Federal Government gave up plans to build 36 more reservoirs in the headwaters of the Mississippi, St. Croix, and Chippewa Rivers. Intense logging moved to Lake of the Woods, where the Corps sent a dredge to improve Warroad Harbor.