The number of unauthorized tunnels discovered through the U.S.–Mexico border has risen dramatically since the mid-1990s. These tunnels are problematic for the state because the subterranean border is both less visible and more difficult to monitor and control than is the surface border. In this era of heighten security, the debate on secure borders has intensified. As a result, the need to demonstrate security success at both the national and the agency level has risen. Efforts to make tunnel discoveries (and security) visible are made within border-security agencies and within national discourse and legislation. These efforts spatially fix tunnels to the border in ways that obscure fuller a understanding of drug trafficking in general. This paper employs archival research, content analysis, and informal interviews with security-enforcement agents to consider the material presence of tunnels within border landscapes.