Given that Lewis and Clark remain so famous, it was inevitable that the other American explorers would be overlooked, particularly William Eaton, the hero of the Battle of Derna in the Barnaby Wars, and Zebulon Montgomery Pike, the explorer of the Mississippi. In the case of Pike, Orsi suggests that the explorer is overlooked and in some cases slighted due to what the expeditions did and did not accomplish. Eaton and Pike represented "the first wave of Manifest Destiny, expanding the republican principles of liberty and citizenship in the world."[1]

Contrasted to that patriotic sentiment are caveats and questions. The career of Zebulon Pike was "dominated by ambiguously motivated explorations of the American West."[2] With the procurement of the Louisiana Purchase, which doubled the size of the nation, Pike had the full force of American authority at his disposal, and his travels through the Colorado Rockies into New Mexico pushed the boundaries between America and Spain. Captured by Spanish officials for illegal entry, he was finally released back into American custody after a year's time with a volume of new information on Spanish territory, its economy, and its military configuration. This sparked a debate about whether the capture was planned by the American government itself.

Pike's return is still debated, as is his relationship with General James Wilkinson and Aaron Burr. The controversy is relevant to Burr's alleged conspiracy to establish a competing empire in the American Southwest, or perhaps as a way of conquering Spanish America without involving the White House. Pike's papers, confiscated by the Spanish, have complicated the search for the truth, and any evidence of his complicity remains confidential, in part because of the unpredictable explorer's unpredictable demise.