Directly across the Fortymile River from the Forty Mile townsite was Fort Constantine, the first North-West Mounted Police (NWMP) post in the region, established 1895. Both are archaeological sites and are co-managed by Yukon government and Tr’ondëk Hwëch’in. In 1893, the North American Trading & Transportation Company constructed Fort Cudahy on the west bank of the Yukon River, just downstream from the Fortymile River. The site was divided into a commercial area, which included several large sawhorses associated with the mill, a dog yard, and a smaller residential area. It included a store, warehouses, a sawmill, and a dozen or so cabins.Fort Cudahy was abandoned about ten years later. Fort Cudahy highlights the changes in economy and the First Nations relationships with the traders, from the equal and collaborative interchange that occurred at Fort Reliance to the trader’s new interest of providing goods that met the miners’ needs.

The Yukon’s first NWMP detachment was built in 1895, approximately 200 metres southwest of Fort Cudahy, over a short summer season, and consisted of a complex of buildings that once included a guard room, staff-sergeant’s quarters, two officers’ quarters, assistant surgeon’s quarters, hospital, office, storeroom, carpenter’s shop, washroom, and a building containing the barracks room, mess hall, and kitchen, built around a parade square and partially enclosed by a log palisade. The Fort was occupied by the NWMP for a short time and by 1901, the much-reduced force at Fort Constantine had moved to the two-storey timber building in the Forty Mile settlement. After its active period between 1895 and 1901, the site was subject to melting permafrost, flooding, and scavenging and deteriorated quickly. The physical remains of Fort Constantine are entirely archaeological.