The lake formed when the Mississippi, a successor to the glacial river, was partially dammed by a delta from a tributary stream and spread out across the ancient valley.

[3] The wide area of the lake stretches from Bay City, Wisconsin, in the north, down to Reads Landing, Minnesota, in the south.

Both were former racetracks for the premier passenger trains of their owners, and the CP rails still carry Amtrak's Empire Builder between Chicago and the Pacific Northwest.

Maiden Rock, on Lake Pepin, is one site said to be the locale where a Dakota woman named Winona leapt to her death.

Over a long period of time, the deep valley was partially filled with sediments, forming a broad floodplain.

Some theorize the lake is filling in at a rate of ten times greater than pre-colonization, due largely to increased run-off from farms along the Minnesota River.

In 1727 René Boucher de La Perrière and Michel Guignas built Fort Beauharnois on the lake.

Large rafts were assembled at Reads Landing at the southern end, and towed downstream to mills at Winona and St.