The lake before the marsh: how the plain was laid

GLACIAL LAKE KANKAKEE AND THE OUTWASH, AT THIS GROUND'S SIZE

The marsh was a lake first, and the lake was the ice's leaving. As the Michigan, Saginaw, and Huron-Erie lobes of the Wisconsin glaciation stood at their moraines — the Valparaiso moraine on the north, the Maxinkuckee on the east and southeast — their meltwaters ponded in the valley between, forming the glacial Lake Kankakee of about 14,000 years ago, held at its level by the limestone ledge at Momence. The lake drained about 13,000 years ago down to the ledge's level, and the ledge held the water table there ever after: the marsh is the lake's unemptied remainder. The physiographic record states the plain's character exactly: M. T. Bushnell's physiography of the Kankakee region (Proceedings of the Indiana Academy of Science, 1927) describes the basin plains as "lacustrine deposits of a shallow glacial lake," the valley itself about five miles wide at this end, narrowing to two or three at the state line, its cross-sections reading "like lake cross-sections" rather than a river valley's — a floor so flat that through St. Joseph County the river falls only about a foot to the mile. The sand the meltwater spread was reworked by wind into the ridges and dunes that stood as islands in the marsh — the "sand islands" of the early record — and the townsite stands on the plain's eastern margin where the sand meets the till uplands: dry ground, thicket-grown in 1854, at the edge of a basin that was water. Chapman's physical chapter draws the larger frame in one line: the watershed divide between the St. Joseph and Kankakee systems runs through this county, so close do the two rivers rise that a mill-race was once dug from the Kankakee's head to the St. Joseph at South Bend and the water made to flow both ways. The glacial frame at county depth — the lobes' meeting over the county, the buried bedrock the drift conceals, the moraine systems by name — is Before the City's and the sister legs', carried there at full strength and pointed to here; this ground's share is the plain, the lake floor, and the ledge, and they are the whole explanation of everything the drainage era had to undo.