Between the 1970s and 1990s, Los Alamos National Laboratory built and utilized a largely custom computer network for the Lab’s supercomputers. Designed to support the unusual performance, storage, and security requirements of an American weapons lab, the Los Alamos Integrated Computer Network, as the focus of historical study, complicates and enriches the history of computer networking development, exploring the approaches and contributions to computer networking of an institution outside the better-known worlds of industry, academia, and the military. For example, the Lab’s reticence to adopt TCP/IP due to performance and security concerns further complicates the narrative of the ARPANET/Internet protocol suite’s adoption among advanced networking sites in the 1980s and 90s.