Toward the end of the Pleistocene, a lobe of the Wisconsin Glacier pushed southwestward into northeast Indiana. Its maximum extent was reached about 22,000 years ago and, as it retreated toward Ohio and Canada, it left a series of terminal moraines in its wake. The last of these in Indiana was the Ft. Wayne Moraine, which curved through the present day city of Ft. Wayne, extending northward and southeastward from that site.
As the Ice Sheet melted from the region, Glacial Lake Maumee formed behind the Ft. Wayne Moraine. West of the Moraine, the ancestral St. Joseph and St. Marys Rivers merged to form the Little River, which flowed southwestward to join the Wabash just west of Huntington, Indiana. Then, about 14,000 years ago, Lake Maumee breached the Ft. Wayne Moraine, sending a torrent of glacial meltwater through the Little River Valley and thence down the Wabash to the Ohio River.
As the Wisconsin Glacier continued to retreat into Canada and the St. Lawrence Seaway opened, the Great Lakes drained to the east; in concert, their surface areas decreased and the region began to rebound from the weight of the Ice Sheet. A vast Lake Plain with extensive swamps and inland dunes developed across northeastern Ohio and the Maumee River cut its way upstream, capturing tributaries north and east of Ft. Wayne (including the St. Marys River). Deprived of these headwater streams, flow through the Little River was greatly diminished and this stream now meanders through a broad floodplain of wetlands, the remnant path of the Maumee Torrent.