The Oregon question was a matter of diplomatic concern starting with the first European exploration of the area. The two countries with the greatest interest were Britain and the United States, although both Spain and Russia viewed themselves as having some claim to the Oregon territory. The first British contact with the Oregon country took place in 1778, when Captain James Cook sailed along the coast of present-day Oregon and Washington states on his third expedition. His mission was to find the western end of the supposed Northwest Passage, but he was unable to do so, since there was none. Captain George Vancouver took a closer look at the coastline that Cook has discovered on a mission between 1792 and 1794. Alexander Mackenzie took a small party across the Rockies and through some of the upper reaches of the Fraser River in 1793. Cook had missed the mouth of the Columbia, so it became the honor of the first American explorer, Captain Robert Gray, to locate it in 1792. The Corps of Discovery of Meriwether Lewis and William Clark came down the Columbia to its mouth on the Pacific, where they spent the 1805-1806 winter. Later, in 1811, John Jacob Astor established a trading post for his Pacific Fur Company at present-day Astoria. The company was forced out during the War of 1812, but was restored with the Treaty of Ghent. Spain and Russia were removed from the picture within a few more years. The Spanish gave up their rather weak claims under the Transcontinental Treaty in 1819, which also established American sovereignty in Florida. The Russian Czar Alexander I attempted to use a ukase to monopolize commerce, whaling, and fishing from Bering Strait south to the 51st parallel. Secretary of State John Quincy Adams warned Russia that the United States opposed any further colonial expansion by Europeans and the Monroe Doctrine clarified this even further. For about two decades, Britain and the United States maintained an uneasy division of control in the Oregon territory, generally permitting one another to conduct business. The British were primarily interested in fur trading, where they were much more prominent than the Americans. However, Oregon began to beckon Americans seeking new lands to settle. In 1834, Jason Lee established a mission station in the Willamette Valley. The Oregon Trail created an influx of settlers, starting with small number in 1839 and growing rapidly from 1843 on. The Oregon Question became a matter of national concern and the 1846 slogan "Fifty-four forty or fight" expressed the opinions of many Americans in favor of strong action to ensure American claims. The final resolution came with the Oregon Treaty, which was signed on June 15, 1846. It provided for the international boundary to extend on the 49th parallel to the middle of Georgia Strait between the mainland and Vancouver Island, and from their around the tip of the island along the middle of the Strait of Juan de Fuca. Apart from the minor "Pig War" later in the San Juan Islands, this concluded the Oregon Question.