From 1967 to 1975, a single, giant, interconnecting machine linked together the vast majority of power users in North America. Called the grid, this collection of generators, transmission lines, substations, and related infrastructure operated in near-perfect synchrony to deliver electricity across the continent. Many had envisioned a coast-to-coast grid for decades, but the project was hindered by cost, competing jurisdictions, a wide array of stakeholders with nonaligned interests, and especially technological barriers. Building this machine was an engineering accomplishment of the highest order. But operating the machine was another matter. Though brief within the now long history of electrification, this eight-year period marked a pinnacle of achievement for American engineers and system operators and a phase of instability for the machine itself.