The Lewis overthrust, famous structural geological feature, extends from Glacier National Park in Montana some 350 miles north into Alberta, Canada; is from 15 to 30 miles wide; and is believed to have been thrust eastward some 35 miles. This is often referred to in texts as a classic example of a large overthrust, but only one of many such observed throughout the world. Evidence for such overthrusting usually offered, is the inverted order of the fossil sequence in the strata, according to the assumed evolutionary advance of biological life during the geological ages, and so contained in the time-stratigraphic rock sequences from older to younger rocks. In the case of the Lewis overthrust rock formations, the so-called "older" algal fossils are confined to the Precambrian Belt series of rocks, which lie above the so-called younger Cretaceous rocks, so correlated because of the index Cretaceous fossils they contain. Such confidence have paleontologists and stratigraphers had in the correctness of their evolutionary hypothesis that in many cases little effort has been spent in examining the physical evidences accompanying such overthrusting. Some field work has been performed during the summer of 1968 in attempting to overcome this deficit. So far such investigations have failed to turn up any pronounced evidence to uphold the hypothesis of a Lewis Overthrust. Photographs of contact lines indicate that the Precambrian strata were water deposited on top of the Cretaceous.