With the Treaty of Guadalupe Hidalgo in 1848 and the Gadsden Purchase of 1853, the United States acquired its last lands to comprise the lower forty-eight states. By the early twentieth century, immigrants to the region performed the everyday labor of cultural imperialism. This article examines the lives, memoirs, and novels of two prolific but unknown immigrants who moved to New Mexico’s Mesilla Valley: Benjamin J. Viljoen and Edith M. Nicholl. Viljoen, a general from the Boer Republics, emigrated in 1903 after suffering defeat by the British Empire in the South African War. He wrote memoirs, articles, and novels relating to the war and his exile in the borderlands. Nicholl, a farmer and writer from an elite British family, first moved to Virginia and then to New Mexico in 1896. Her imperial pedigree gave her a unique perspective of the Mesilla Valley. When placed together, the lives and writings of Viljoen and Nicholl not only reveal the everyday imperial cultures in the Southwest; they testify to the subjectivity of frontier life, its gendered spaces, and its transmutability on both sides of the Atlantic.