Lake Pepin is a naturally occurring lake, and the widest naturally occurring part of the Mississippi River. It is a widening of the river on the border between Minnesota and Wisconsin. The formation of the lake was caused by the backup of water behind the sedimentary deposits of the Chippewa River’s delta. It has a surface area of about 40 square miles (100 km2) and an average depth of 18 feet (5.5 m), which makes it the largest Lake on the entire Mississippi River.

The wide area of the lake stretches from Bay City, Wisconsin, in the north, down past Pepin, Wisconsin, and Reeds Landing, Minnesota, in the south, with Pepin being just upstream from where the Chippewa River enters the Mississippi. The villages of Maiden Rock and Stockholm border on the Wisconsin side, while Frontenac State Park takes up a large part of the Minnesota side. The largest city on the waterfront is Lake City, Minnesota.

Lake Pepin – MN DNR Site