The most important effect of the expedition was to give currency to
Long's description of the country through which he passed as the
"Great American Desert," unfit for cultivation and uninhabitable by
agricultural settlers. The whole of the region between the Missouri
River and the Rocky Mountains seemed to him adapted as a range for
buffalo, "calculated to serve as a barrier to prevent too great an
extension of our population westward," and to secure us against the
incursions of enemies in that quarter. [Footnote: Long's Expedition
(Early Western Travels, XVII.), 147, 148.] A second expedition, in
1825, under General Atkinson and Major O'Fallon, reached the mouth
of the Yellowstone, having made treaties with various Indian tribes
on the way.

In the mean time, Congress and the president were busy with the
question of Oregon. By the convention of 1818, with Great Britain,
the northern boundary of the United States was carried from the Lake
of the Woods to the Rocky Mountains, along the forty-ninth parallel.
Beyond the mountains, the Oregon country was left open, for a period
of ten years, to joint occupation of both powers, without prejudice
to the claims of either. Having thus postponed the Oregon question,
the secretary of state, John Quincy Adams, turned to his Spanish
relations. Obliged by Monroe to relinquish our claim to Texas in the
treaty of 1819, by which we obtained Florida, he insisted on so
drawing our boundary-line in the southwest as to acquire Spain's
title to the Pacific north of the forty-second parallel, and to the
lands that lay north and east of the irregular line from the
intersection of this parallel with the Rocky Mountains to the
Sabine. Adams was proud of securing this line to the Pacific Ocean,
for it was the first recognition by an outside power of our rights
in the Oregon country.[Footnote: Treaties and Conventions (ed. of