As a fundamental system for protecting the rights and interests of teachers, the university tenure system plays a crucial role in the development of universities in the United States. The tenure system has developed and evolved over a long period of time, from the dual track system of university teachers under church management in the 17th century to the formal establishment of the university tenure system in the 20th century and then to the “up-or-out” policy in the 21st century. The foundation of this system’s development has always been maintaining teachers’ academic freedom and guaranteeing their livelihoods. This article explores how universities and related institutions in the United States have integrated the protection of teacher academic freedom and economic security throughout the development of higher education by studying the development of the US university tenure system.