The Foothills erratics train of Alberta was carried into place during coalescence between montane glaciers and the Laurentide ice sheet. Its age has been controversial: Late Wisconsinan and pre-Wisconsinan ages have been assigned to it. Cosmogenic 36Cl exposure dating was carried out on erratics over a 130 km segment of the erratics train. Seven of eight age determinations support emplacement during the late Wisconsinan glaciation. These ages eliminate the possibility of an ice-free corridor during the last glacial maximum. They are also consistent with the hypothesis that the Laurentide ice sheet was the most extensive of all Pleistocene continental ice sheets in western Canada.