These falls were the only major waterfall on the nation’s great river, the Mississippi, and until locks opened in the 1960s, were the limit of travel on the river. The falls, altered by dams, spillways, locks, and other control structures, are the reason why Minneapolis is there, and why the Twin Cities emerged as one of the economic centers of the nation (home to the headquarters for General Mills, Cargill, 3M, and more recently retailers like Target and Best Buy). Grain silos and flour milling plants are still visible on either side of the falls, remaining from the city’s role as the processor for the wheat fields of the upper Midwest. The large Gold Medal flour mill on the west side of the falls is now a museum, and the General Mills complex on the east side of the river is being turned into condominiums.