Sailboats, Lake Minnetonka, Minnesota, 1975Photograph by David BoyerSailboats jockey for position in a boat race on Lake Minnetonka in Minnesota, a state that owes much of its buoyant outdoor spirit to its rivers and 15, 291 lakes. For a lake to be counted, it has to cover at least ten acres (four hectares) and flow with fresh water. No ponds or potholes, please.