Pike was an American Army officer, as was his father. He grew up on Army outposts in Ohio and Illinois, then the western edge of the growing United States. In 1799, he was commissioned a second lieutenant and was promoted to first lieutenant in the same year.
Pike’s entire career, like his childhood, was focused on the American frontier. In 1805, he was asked to find the source of the Mississippi River, in the north of the Louisiana Territory that was now the possession of the United States. He was also supposed to encourage any French or Canadian traders and trappers on US land to follow US law.
Pike and his men travelled upstream, reaching the confluence of the Mississippi and Minnesota rivers on September 21. There he negotiated a purchase of land from local Dakota bands; the site would become Fort Snelling. They wintered at the mouth of the Swan River, near present-day Little Falls, waiting for the river to freeze. They continued on the ice in early December, visiting British North West Company fur posts, finishing at Leech Lake outpost. After raising the American flag over that station, they retraced their steps, returning to St. Louis on April 20, 1806.
After this successful venture into the US’ new land, Pike was almost immediately told to set out again. Having followed the Mississippi, he was now to seek out the headwaters of the Arkansas and Red Rivers, as well as to assess natural resources and establish friendly relations with local tribes. He left on July 15, 1806. They made their way across what is now Texas and the southern Great Plains to the Rockies. By November, he and his men were trying to summit Pike’s Peak, the over 14,000-foot mountain named for Pike.
As they moved south, the Spanish captured Pike’s party, as they had crossed into Spanish territory. The Americans were taken to Santa Fe and then to Chihuahua. While there, Pike stayed with Juan Pedro Walker, who confiscated his maps and journal to translate them. However, Pike also had access to Spanish maps while there. When released, he left with a better cartographic understanding of the Southwest. Pike and most of his men were deposited on the Louisiana border on July 1, 1807.
Pike might have been released by the Spanish, but his journals were not. They were not returned to the United States until the twentieth century. Instead, Pike wrote an account from memory, which was published in 1810. It was a popular read and was translated into Dutch, French, and German. In the book, Pike reflected on Mexican discontent with Spain and trade between New Mexico and Chihuahua (the Santa Fe Trail).
After these expeditions, Pike was quickly promoted during the War of 1812. He was made brigadier general in March 1813. A little over a month later, he was killed during an attack on York (Toronto).