Ralph Emerson Twitchell's The History of the Military Occupation of the Territory of New Mexico is an authoritative account of the U.S. military's role in the annexation and governance of New Mexico during the mid-19th century. Meticulously researched and rich in detail, Twitchell's work chronicles the military occupation that followed the Mexican-American War and its profound impact on the region's social, political, and cultural landscape. The book begins with an exploration of the events leading to the Treaty of Guadalupe Hidalgo in 1848, which transferred New Mexico from Mexico to the United States. Twitchell delves into the challenges faced by military authorities as they sought to establish control, maintain order, and integrate the territory into the expanding United States. He examines conflicts with Native American tribes, tensions with local Hispanic populations, and the strategic importance of New Mexico as a gateway to the American West. Twitchell's analysis includes firsthand accounts, official reports, and historical documentation, offering a comprehensive perspective on this pivotal period. He also explores the personalities of key military and political figures, shedding light on their decisions and the lasting consequences of their actions. The History of the Military Occupation of the Territory of New Mexico is an invaluable resource for historians, military scholars, and anyone interested in the complexities of U.S. expansionism. Twitchell's work remains a cornerstone in understanding the transformative era that shaped the Southwest's path to statehood.