The book "Expeditions of Zebulon Montgomery Pike, Volume 3 (of 3). To the upper Mississippi River through the territory of Louisiana and in New Spain during the years 1805-6-7" is a valuable document of the journey of the American military officer and explorer Zebulon Montgomery Pike in the early XIX century. In this book, the author describes in detail his journey to study the territories of the southwestern United States and Mexico. Pike recounts the hardships and trials he and his crew endured during this long journey. He describes in detail the geography, flora and fauna of the areas they explored, as well as encounters with the local inhabitants. In addition, the book contains cartographic materials that help the reader better imagine Pike's journey. "The Expeditions of Zebulon Montgomery Pike, Volume 3" is an unforgettable journey into the past, which provides an opportunity to better understand the history of exploratory voyages and study the American continental territory in the early period of its formation.