The following was the author’s presidential address at the annual meeting of the Pacific Coast Branch, American Historical Association, in Northridge, California, on August 4, 2017. The twentieth-century visual history of the U.S.-Mexico borderlands, la frontera, offers a rich set of representations of the shared border environments. Photographs, distributed in the United States and in Mexico, allow us to trace emerging ideas about the border region and the politicized borderline. This essay explores two border visualization projects—one centered on the Mexican Revolution and the visual vocabulary of the Mexican nation and the other on the repeat photography of plant ecologists—that illustrate the simultaneous instability and power of borders.