The government of the United States maintained special interests in Oregon. It founded its claims on the "doctrine of the right of discovery." Although Robert Gray was a mariner for a private fur-trading company, he sailed under a sea letter issued by President George Washington. His crossing of the bar of the Columbia initiated the U.S. claim to having "discovered" Oregon. The Lewis and Clark Expedition was a military expedition financed and directed by the government. Fort Clatsop, though occupied less than five months in 1805-06, was deemed an American outpost. So, too, the Pacific Fur Company's Fort Astoria was an American venture, and the U.S. through the actions of Captain Biddle and John Prevost asserted national interests in 1818 pursuant to the terms of the Treaty of Ghent.
In 1818 the United States and Great Britain met in diplomatic conference to try to resolve their interests in the Oregon Country. The negotiators, at loggerheads over the extension of the 49th parallel to the Pacific, reached a compromise. In the Convention of 1818 they agreed to shared spheres of interest in the Columbia watershed, deferring the question of sovereignty for the time being.
The Americans were not idle. In the 1819 Adams-Onis Treaty, whereby Spain ceded Florida to the U.S., American negotiators secured all of the Spanish "discovery rights" north of the 42nd parallel--the northern boundary of California. In 1824 the United States negotiated an agreement permitting trade for ten years in Alaska and fixing Russia's southern boundary at 50° 40'. Slowly, steadily, the United States had narrowed the field among the nations vying for control of the Oregon Country. Great Britain, the United States, and the Indian tribes remained as competitors. In 1827 the two countries agreed to extend indefinitely their earlier agreement that each had a sphere of interest in the region. The new condition added to the convention was that either nation might give notice and demand a resolution of the issue within one year.
American "discovery rights" gained Supreme Court sanction when, in 1823, Chief Justice John Marshall ruled in a matter involving former Indian lands. Marshall opined in Johnson v. McIntosh that because natives were wanderers over the face of the earth, their rights were impaired and subordinate to the "discovery rights" of Europeans. While tribes retained an occupancy right, title was not vested in them. The Marshall ruling became a convenient justification to dispossess hundreds of tribes of their homelands.
President Andrew Jackson, an expansionist with interests in the West, attempted in 1835 to purchase the harbor of San Francisco for $500,000 from Mexico. The following year he dispatched the brig Loriot to the West Coast. Lieutenant William A. Slacum carried a presidential commission to examine Puget Sound, the Columbia estuary, and San Francisco Bay, assess those anchorages for strategic value, and examine the frontier economy of the region. Slacum's report, printed in the United States Congressional Serial Set, made a strong case for American acquisition of all three harbors.
Jackson next endorsed and Congress funded the multifaceted U.S. Exploring Expedition. Under the command of Lieutenant Charles Wilkes, this Navy party included five vessels, more than 300 seamen, and a corps of talented scientists, artists, and officers. After exploring the coasts of South America, Australia, and Hawaii, the expedition in 1841 sailed to Puget Sound and the Columbia River. Overland parties traveled south via the Cowlitz to Fort Vancouver, east through the Gorge to Fort Walla Walla, and south through the Willamette Valley to Sutter's Fort on the Sacramento River. James Dwight Dana collected fossils at Saddle Mountain at the mouth of the Columbia; Titian Ramsay Peale sketched the Umpqua Mountains; Horatio Hale compiled Indian vocabularies; and Charles Wilkes penned a fact-filled description of western Oregon.
In 1845 the narrative and scientific reports of the Wilkes Expedition, as it was popularly called, began to appear. Volumes four and five contained candid information about Oregon. Wilkes described the Willamette Valley and its "advantages for raising crops, pasturage of stock, and the facilities of settlers becoming rich." He wrote: "The salmon-fishery may be classed as one of the great sources of wealth, for it affords a large amount of food at a very low price, and of the very best quality . . . ." The sixth volume of reports, an atlas, included numerous charts of Puget Sound and the Columbia River useful for mariners. Over the next dozen years, specialists wrote scientific assessments of the flora and fauna collected by the expedition and published 14 oversized folios of hand-colored illustrations of the specimens. The knowledge about Oregon had increased dramatically and was based on sound authority.
While the Wilkes party was on the high seas headed to the Pacific Northwest, Robert Greenhow, librarian to the Department of State, compiled his Memoir, Historical and Political, on the Northwest Coast of North America (1840). Senator Lewis Linn of Missouri had the report printed for the Select Committee on Oregon Territory and requested the immediate publication of an additional 2,500 copies for the Senate to distribute. Greenhow presented a history of exploration, covered the diplomacy of sovereignty issues, discussed the fur trade, and argued that Oregon was a region "lying entirely within the undisputed limits of the Republic." Therein he revealed his agenda. Greenhow's memoir was a brief to make the case for American sovereignty over the Pacific Northwest.
Thomas Hart Benton, senator from Missouri and for more than 20 years a champion of American expansion, in 1842 secured congressional funding for his son-in-law, John Charles Fremont, to explore west to South Pass. The following year Fremont, a member of the U.S. Topographical Engineers, set out again, guided by Kit Carson, to follow overland emigrants across the Oregon Trail. Fremont kept a diary and collected minerals, plants, and zoological specimens. Charles Preuss, his cartographer, prepared eight detailed strip maps showing the route of the trail to Fort Walla Walla. In the map margins were notations on fords, grazing sites, camping locations, and the availability of firewood. Fremont's wife, Jessie, turned her husband's diaries into flowing prose. Published by the Government Printing Office in large numbers, the Fremont narratives and Preuss maps became a major publicity piece for Oregon and a virtual travelers' guide to the trail.
In early 1846 Lieutenant Neil M. Howison sailed to Oregon on the Shark to carry out another reconnaissance. Delayed by the wreck of the ship on the Columbia bar, Howison sojourned for five months and examined the land, interviewed residents, visited Indian villages, and reflected on what he saw. He noted that the influence of Dr. John McLoughlin had "done more than any other man toward the rapid development of the resources of the country." Howison described wolves, grizzly bears, elk, and the thriving condition of cattle and sheep. "I can think of nothing vegetable in nature," he commented, "that Oregon will not produce." His report was ultimately issued in the United States Congressional Serial Set in 1848. It was another candid assessment of Oregon by an objective observer.
During the period 1792 to 1846, the U.S. government thus aided and abetted American interest in Oregon. The nation's leaders, both public and private, took actions to help buttress claims to Oregon through discovery, diplomacy, exercise of will, and the persuasive historical research of Robert Greenhow. The explorations of Lewis and Clark, Slacum, the Wilkes expedition, John Fremont, and Neil M. Howison generated maps, reports, and collections of specimens. These were analyzed and published. The evidence was growing about the prospects of the Pacific Northwest, and Oregon in particular.