The Administrative Procedure Act (APA) of 1946 celebrated a milestone birthday this year. Its requirements—that regulations be grounded in statutory law and an administrative record that includes public notice-and-comment—have guided executive branch rulemaking without significant amendment for 75 years. It is one of the most important and enduring pieces of legislation ever enacted, yet its passage wasn’t always assured. This commentary, excerpted from my recent Daedalus essay on “Milestones in the Evolution of the Administrative State,” reviews the contentious and messy, yet constructive, process that yielded this landmark act.