“The Mexican Frontier, 1821-1846: The American Southwest Under Mexico” by David J. Weber is a comprehensive textbook that delves into the history of the American Southwest during the early 19th century. Published in 1982 by the University of New Mexico Press, this 440-page trade paperback explores the complex relationships between the United States and Mexico in the region, focusing on the sociopolitical dynamics of the time. With a specific focus on the Southwest states of Arizona, New Mexico, Oklahoma, and Texas, this book is a valuable resource for those interested in United States history, particularly in the 19th century.