Through careful examination of primary documents, this book reveals that the true purpose of Zebulon Pike's western expedition in 1806-1807 was not innocent exploration of the West but an espionage mission in preparation for an American invasion of New Mexico. In 1806, the United States was on the brink of war with Spain over the disputed western boundary of the Louisiana Purchase and anticipated invading New Mexico. Possessing only meager information on the terrain as well as Spanish troop numbers and fortifications, President Thomas Jefferson and General James Wilkinson needed an agent who could cross the continent to Spanish territory all the way to the capital of Santa Fe, provide a plausible "cover story" for being there, and return with the vital information. Zebulon Pike: Thomas Jefferson's Agent for Empire is the story of how Pike carried out his mission as a prelude to an American invasion of New Mexico. This unique book is the first to fully chronicle Pike's 1806-1807 expedition to the Rocky Mountains and beyond, addressing both the exploratory and the clandestine purposes of Pike's western journey. By carefully examining the evidence available in primary documents, which shows that Pike prepared and carried a map showing a route to Santa Fe on his journey, the author overturns the conventional wisdom that Pike became lost searching for the Red River and mistakenly wandered into Spanish territory. This book also presents the Spanish perspective and response to Pike's invasion of Spanish territory and provides historical context to understand the role of Pike's expedition in Thomas Jefferson's quest to build an American "empire for liberty."