Following the start of the Lewis and Clark expedition, further exploration of the Louisiana Territory was undertaken by Lieutenant Zebulon Pike. In the fall of 1805, the military commander of Louisiana, General James Wilkinson, ordered Pike to explore the headwaters of the Mississippi River. The source of the Mississippi was important to find because it would mark the latitudinal boundary between Canada and the US. However, due to poor planning, Pike ended up in Minnesota in the middle of winter, lost among the snowy forests and lakes. If not for two British fur-traders who, illegally trespassing on US land, found him, he may have died. He returned to St. Louis unsuccessful.
Despite this failure, Wilkinson dispatched him again in August 1806, this time to explore the headwaters of the Arkansas River. Pike successfully followed the Arkansas to its source in the mountains of what is now southern Colorado. However, after that, he inexplicably turned southward, heading toward the headwaters of the Rio Grande. He was captured wandering around the desert by Spanish troops, who brought him to the Louisiana border and returned him to the embarrassed Wilkinson. This marked the end of Pike's explorations.
Other than a rise in exploration, an immediate consequence of the Louisiana Purchase was the heightening of tensions with Spain. The treaty that granted the Louisiana Territory to the US defined the territory vaguely, as "Louisiana with the same extent as it now has in the hands of Spain, and that it had when France possessed it." The original Louisiana Territory had encompassed land to both the west and east of the Mississippi River. In 1763, the portion of Louisiana to the east of the Mississippi had passed into British hands, while the portion to the west passed into Spanish hands. At the same time, Britain had acquired Florida from Spain, and united East Florida, which had been Spanish, with and West Florida, which had been French and a part of the original Louisiana. In 1783, Britain surrendered both Floridas to Spain, and ceded its portion of the original Louisiana to the US. So the question was: was West Florida a part of the Louisiana Territory under the definition of the treaty, since it had been part of the original French Louisiana? If so, had the US bought it?
When James Monroe and Robert Livingston, the American brokers of the Louisiana Purchase, asked French foreign minister Charles de Tallyrand whether or not West Florida was included in their purchase, he responded cryptically, "Gentlemen, you have made a noble bargain for yourselves, and I suppose you will make the most of it." Monroe and Livingston took this answer to mean they controlled West Florida, and this became official administration policy. Spain, for its part, regarded the entire Louisiana Purchase as illegal, since Spain's previous treaty with Napoleon had stated Louisiana would not be sold. If the Spanish had to give up their lands in the west, however, they certainly did not want to let West Florida go. At the suggestion of the French, they retaliated against the policy of the administration by attacking American merchants at sea.
Coming at a time of tension between the United States and Spain, there is much speculation that Zebulon Pike's second exploratory mission may have simply been a cover for an espionage mission to investigate Spanish positions in the West. It was known that General Wilkinson was frequently involved in intrigue both for and against the Spanish, and many historians believe that this was the true purpose of Pike's expedition. His turn to the south, more than anything else, suggests espionage as his motive. An experienced explorer, Pike would have surely realized once he got to the headwaters of the Rio Grande that he was on waterways that flowed directly into the gulf. This would have signaled to him that he was outside of American Louisiana, and he could have returned directly to US territory. The official story, that he had lost his way again, earned him the nickname "the lost pathfinder." He returned to St. Louis, where he published an account of his travels and received more fame than even Lewis and Clark. Whatever his true motives were, Pike was the first to thoroughly explore the southern Rockies, and the maps he drew proved invaluable to future explorers and settlers of the southern Louisiana Territory.
If Pike's journeys were undertaken with the goal of espionage, his amateurish mission would have served as the US's grossly incomplete introduction to the realm of European power politics in regard to North America. While the US had always been heavily involved in diplomacy with the other nations that occupied areas of North America, and consistently taken action to protect its interests, Thomas Jefferson was the first President to be treated to the full experience of international intrigue and manipulation. Though the Louisiana Purchase had ejected France from a geographically large part of North America, Napoleon Bonaparte and Charles de Tallyrand proved continually that the French influence in affairs on the North American continent had not decreased commensurately.