King of Prussia Mall is usually accepted as the largest mall in the United States. Obviously Minnesota's Mall of America takes up more space, but King of Prussia's nearly 2.8M square feet of leasable space puts it at the top of the list by about 15,000 square feet.
Soon there may be no debate as Simon Property Group plans to begin construction on a 250,000 square foot addition. Currently detached, King of Prussia Mall is not one contiguous space. IMC Construction will be connecting the Plaza and the Court.