As we have seen, President Jefferson, whose master mind organized and devised this expedition, had dwelt longingly on the prospect of crossing the continent from the headwaters of the Missouri to the headwaters of the then newly-discovered Columbia.  The route thus explored was more difficult than that which was later travelled by the first emigrants across the continent to California.  That route lies up the Platte River, through what is known as the South Pass of the Rocky Mountains, by Great Salt Lake and down the valley of the Humboldt into California, crossing the Sierra Nevada at any one of several points leading into the valley of the Sacramento.  The route, which was opened by the gold-seekers, was followed by the first railroads built across the continent.  The route that lay so firmly in Jefferson’s mind, and which was followed up with incredible hardships by the Lewis and Clark expedition, has since been traversed by two railroads, built after the first transcontinental rails were laid.  If Jefferson had desired to find the shortest and most feasible route across the continent, he would have pointed to the South Pass and Utah basin trails.  But these would have led the explorers into California, then and long afterwards a Spanish possession.  The entire line finally traced over the Great Divide lay within the territory of the United States.

But it must be remembered that while the expedition was being organized, the vast Territory of Louisiana was as yet a French possession.  Before the party were brought together and their supplies collected, the territory passed under the jurisdiction of the United States.  Nevertheless, that jurisdiction was not immediately acknowledged by the officials who, up to that time, had been the representatives of the French and Spanish governments.  Part of the territory was transferred from Spain to France and then from France to the United States.  It was intended that the exploring party should pass the winter of 1803-4 in St. Louis, then a mere village which had been commonly known as Pain Court.  But the Spanish governor of the province had not been officially told that the country had been transferred to the United States, and, after the Spanish manner, he forbade the passage of the Americans through his jurisdiction.  In those days communication between frontier posts and points lying far to the eastward of the Mississippi was very difficult; it required six weeks to carry the mails between New York, Philadelphia, and Washington to St. Louis; and this was the reason why a treaty, ratified in July, was not officially heard of in St. Louis as late as December of that year.  The explorers, shut out of Spanish territory, recrossed the Mississippi and wintered at the mouth of Wood River, just above St. Louis, on the eastern side of the great river, in United States territory.  As a matter of record, it may be said here that the actual transfer of the lower part of the territory—­commonly known as Orleans—­took place at New Orleans, December 20, 1803, and the transfer of the upper part was effected at St. Louis, March 10, 1804, before the Lewis and Clark expedition had started on its long journey to the northwestward.