Beginning about two million years ago, four glaciers covered and reshaped Minnesota, with the last, the Wisconsin glacier, melting about 10,000 years ago and leaving many of the state’s present landforms, including moraines, kames, eskers, drumlins, and the soil beneath its vegetation. Aitkin was built on a moraine, and as glacial ice melted, lakes formed behind these ridges; Glacial Lake Aitkin covered most of northern Aitkin County, including McGregor, stretched from Aitkin to present-day Grand Rapids, and for a time joined Lake Upham. These shallow lakes disappeared when the glacier advanced again, then reformed after its final melting as Glacial Lake Aitkin II and Glacial Lake Upham II, later dividing as outlets drained them. As Lake Aitkin slowly drained, peat began forming in the remaining bog area about 6,700 years ago, eventually accumulating to depths of five to ten feet. The bogs around McGregor contain peat, a mass of dead and decaying plant material that builds up in poorly drained land and old glacial lake beds because stagnant water slows normal decomposition. The United States has 51 million acres of peat, more than seven million of them in Minnesota. Minnesota has three types of peat: fibric, sapric, and hemic, with hemic bogs found in the McGregor area. Peat has been used since Roman times as fuel and also for insulation, surgical dressings, baths for injuries and other medical conditions, sewage treatment, and especially horticulture. Peatlands also produce crops such as wild rice, sod, cranberries, and blueberries, and peat is a major component of potting soil, soil conditioners, and molded pots for seed germination. In Minnesota today, the peat industry generates more than ten million dollars in business, and peat is expected to grow in value as fossil fuels are depleted; peat-burning power plants operate in Finland, Ireland, and Russia, and Maine established a peat-fired power plant in 1990.