Although Spanish seamen had noted the Fraser estuary in 1791, when Alexander Mackenzie reached the upper Fraser in 1793 on his way to the Pacific, he thought he was on the Columbia. Simon Fraser and John Stuart of the North West Company explored the river under the same misapprehension in 1808, realizing only when they reached the sea that two great river system drained the north Pacific slope. Although the Fraser was not throughout its course a practical canoe route, the Hudson's Bay Company integrated it into a new supply system when forced in 1848 to abandon the Columbia. *Note: This designation has been identified for review. A review can be triggered for one of the following reasons - outdated language or terminology, absence of a significant layer of history, factual errors, controversial beliefs and behaviour, or significant new knowledge.