The Source of the Mississippi River:
Pike was sent to Minnesota by General James Wilkinson (Governor of the Louisiana Territory) to search for the source of the Mississippi River in 1805. Pike led a crew of 20 men from St. Louis to upper Minnesota during the fall and winter. They traveled on boats, and then sleds (when the river iced over). Although the actual source is Lake Itasca, Pike was convinced that the nearby Lake Leech was the source.

The Rocky Mountains:
General Wilkinson then sent Pike to the Rocky Mountains and the southwest in 1806, but was officially told not to enter Spanish territory. Pike discovered Pike's Peak in Colorado, but failed to climb it. Continuing south, Pike did enter Spanish territory, and was arrested and taken to Santa Fe (in what is now New Mexico). Pike was one of the first Americans to see New Mexico. He was released by the Spanish in Louisiana. His notes about his journey mistakenly stated that the area he traveled in was mostly a desert, unsuitable for farming. This discouraged the settlement of the area for quite a while, but trade increased and Pike's information on the military weakness of the Spanish was quite important.

General Pike died in 1813 during the War of 1812 at the battle of York (in Canada); Pike commanded the American troops at the battle of York.