The Nipissing phase of ancestral Lakes Michigan, Huron, and Superior was the last pre-modern highstand of the upper Great Lakes. Reconstructions of past lake-level change and glacial isostatic adjustment (GIA), as well as activation and abandonment of outlets, is dependent on an understanding of the elevation of the lake at each outlet. More than 100 years of study has established the gross elevation of the Nipissing phase at each outlet, but the mixing of geomorphic and sedimentologic data has produced interpreted outlet elevations varying by at least several meters. Vibracore facies, optically stimulated luminescence and radiocarbon age control, and ground-penetrating...