The Pigeon River Road
This road was constructed to facilitate the transportation of mail between Thunder Bay and Duluth during the winter months when navigation was closed on Lake Superior. Demands for a reliable year-round mail service arose with the development of the Silver Islet Mine in 1870. A temporary mail trail was opened in 1872 before a 61 km winter road was constructed from Fort William to the Pigeon River by John Carroll in 1873-74. The poorly built road was used by mail carriers until the completion of the C.P.R. to Thunder Bay in 1882. As the area traversed by the road remained sparsely settled, it was little used and much of it was abandoned when the International, or "Scott", Highway (later No. 61) was constructed in 1913-17.
Plaque via Alan L. Brown's site Ontario Plaques. Full page here.