The coastlines of the lakes in Minnesota amount the the most shoreline of any state in the union.
I think Michigan has the most shoreline of any of the 50 US states with the exception of Alaska...
From wikipedia:
Michigan has 64,980 inland lakes. A person is never more than six miles (10 km) from a natural water source, or more than 87.2 miles (137 km) from Great Lakes coastline.
Michigan ranks 2nd in the nation for coastline of any state, behind Alaska. (3288 miles of shoreline)