ABSTRACT: The Copper Harbor Formation (CHF) of Michigan and Wisconsin, USAis subdivided into distinct lithostratigraphic units. We divide the CHF into four formal members. From oldest to youngest are the Great Conglomerate Falls Member (pebble to cobble clast supported conglomerate), the Gorge Falls Member (pebble to boulder clast supported conglomeratewith sandstone lenses, containing two tongues), the Sandstone Falls Member (pebble conglomerate and sandstone, containing two named lenses and one named tongue), and the Union Bay Member (sandstone, containing one named lens). The designation of members will aid in mapping and structural interpretations, as well as future chronostratigraphic work. The largest flows of the Lake Shore Traps (LSTs) are also defined herein and are kept as units within the CHF. They are from oldest to youngest the Potawatomi Flows, Cloud Peak Flows, Brockway Flow, Hunters Point Flows, and Seven Mile Point Flow. The flows are included within the four sedimentary members and the term LSTs remains informal.