The North West Company was unchallenged in the fur trade of the region from 1813 to 1821, when it was merged with the Hudson's Bay Company. During this period the company put into practice the system attempted by the Astorians' Pacific Fur Company. A supply ship arrived each spring at Fort George (Astoria). Fur brigades from the interior of the Columbia and New Caledonia districts would converge on Fort George each spring. Furs were loaded on the ship and supplies carried back to the interior. The ship would then carry the furs to Canton, China, where furs would be exchanged for tea and other goods, which were then carried to Britain, completing a global circuit. Company letters, reports, and personnel were generally conveyed overland along a route between Fort George and Fort William on Lake Superior, making use of Athabasca Pass. Later, under the Hudson's Bay Company, the York Factory Express used this route, reoriented to York Factory on Hudson Bay.