The Oregon Treaty of June 1846, signed in Washington, D.C., by the United States and the United Kingdom, marked the effective end of the old Hudson's Bay Company's jurisdiction of the former western Columbia District / Department on the Pacific coast, although the HBC still continues a mercantile commercial business into the 21st century.

The American short-lived Pacific Fur Company (PFC) of 1810–1813, founded Fort Astoria near the entrance mouth of the long Columbia River waterway to the continental interior and began to compete with and counter the older NWC trade posts.

Funded largely by German-American merchant John Jacob Astor, the company men had previously sailed around Cape Horn on board Tonquin.

Also in 1815 the New Caledonia district began receiving the bulk of its annual supplies by sea from the lower Columbia River rather than overland from Fort William and Montreal.

This "joint occupation" continued until the Oregon Treaty of 1846, yet American attempts to conduct commercial operations in the region failed in the face of competition by the Hudson's Bay Company.

[3] The North West Company found the Native Americans of the Columbia region generally unwilling to work as fur trappers and hunters.

The company depended upon native labor east of the Rocky Mountains and found it difficult to operate without assistance in the west.

For this reason the company began, in 1815, to bring groups of Iroquois, skilled at hunting and trapping, from the Montreal region to the Pacific Northwest.

The Iroquois were intended not only to support company personnel but, it was hoped, teach local natives the skills of hunting and trapping, and convince them to take up the work.

Fort Nez Percés would long remain a strategic site, located at the junction of a variety of trails leading to vastly different regions.

The fort became an important center for the procurement of horses, a base for expeditions far to the southeast, and a focal point for fur brigades preparing to journey through the Columbia River Gorge.

By 1825 there were usually two brigades, each setting out in spring from opposite ends of the route, Fort Vancouver, and York Factory on Hudson Bay, and passing each other in the middle of the continent.

Each brigade consisted of about forty to seventy-five men and two to five specially made boats and traveled at breakneck speed (for the time).

The brigades carried supplies in and furs out by boat, horseback and as back packs for the forts and trading posts along the route.

Between the acquisition of the North West Company in 1821 and the Oregon Treaty of 1846, the HBC greatly expanded the operations of the Columbia Department.

[8] Fort Vancouver was the nexus for the fur trade on the Pacific Coast; its influence reached from the Rocky Mountains to the Hawaiian Islands, and from Alaska into Mexican-controlled California.

[citation needed] The employment of Hawaiian Kanakas was gradually expanded until at least 207 in the Columbia Department by 1845, with 119 located at Fort Vancouver.

The administrative headquarters of fur operations, and of the Columbia Department, then shifted to Fort Victoria, which had been founded by James Douglas in 1843 as a fallback position in preparation for the "worst case" scenario settlement of the dispute, in the face of manifest destiny.

Akrigg coined the term "Southern Columbia" for the "lost" area south of the 49th Parallel, but this has never come into common use, even by other historians.