After the Laurentide Ice Sheet (LIS) reached its maximum extent in North America 18,000 14C yr B.P., it underwent a period of rapid retreat, generating large volumes of meltwater that collected in proglacial lakes along its margin. The largest and most extensive of these was glacial Lake Agassiz, which existed from 11,700 14C yr B.P. to 7,500 14C yr B.P. In 1823, when William Keating first described what became known as Lake Agassiz, the prevailing idea explaining such past lakes was that they were remnants of Noah’s Flood. Keating interpreted the site to be the lakebed of an ancient lake, one of the spillways of which was the Mississippi River and, although he was careful not to make any biblical references to the lake’s formation, he also resisted the interpretation of glacial assistance in formation. Subsequent researchers, such as David D. Owen, George Dawson, and G.K. Warren, agreed with the interpretation of a large lake and although Louis Agassiz’s glacial theory was becoming more accepted, they did not attribute the lake as proglacial. Instead, hypotheses ranged from transportation of glacial drift via floating ice to ponding behind terminal moraines. It wasn’t until 1873 that N.H. Winchell, first state geologist of Minnesota, published his discussion on the work of previous researchers and proposed Lake Agassiz’s proglacial origins.

Lake Agassiz was named in honor of Louis Agassiz in 1880 by Warren Upham, who spent the next couple of decades researching and publishing on the lake for several state and government agencies in the United States as well as Canada. Upham associated the existence of the lake to a single retreating ice sheet, in line with George Dawson’s work on the LIS. In 1895, he published his seminal work, the U.S. Geological Survey’s Monograph 25 The Glacial Lake Agassiz. However, problems arose from Upham’s interpretation of a single filling and draining of the lake. Jospeh Burr Tyrrell published research in 1896 and 1898 that suggested Lake Agassiz formed as a result of action by multiple ice sheets, an interpretation that put Tyrrell at odds with Upham for more than twenty years. Further damage was done to Monograph 25 when William A. Johnston contradicted the “single fill” hypothesis and stated that there had been at least two fillings and drainages of Lake Agassiz. This resulted in Upham publishing his strong disagreement with Johnston’s interpretations and making a public call for support from the geological community. This resulted in a compromise proposed to try to reconcile the interpretations of the two researchers. Unfortunately, this compromise was not based on the geological evidence and set Lake Agassiz research back.