American postulate theory is the body of work of several American mathematicians in the first few decades of the twentieth century, concerned with studying the structure of established mathematical theories by examining fundamental assumptions. They examined alternative postulational formulations and considered desirable features of a postulate system: consistency, independence, completeness, categoricity, brevity. John Corcoran, “On Definitional Equivalence and Related Topics,” History of Symbolic Logic 1 (1980), 231—234, introduced the term “American postulate theory,” identified some of its practitioners and suggested a need for historical study of their work. Michael Scanlan “Who Were the American Postulate Theorists?,” The Journal of Symbolic Logic 56 (1991), 981—1002 and “American Postulate Theorists and Alfred Tarski,” History and Philosophy of Logic 24 (2003), 307-325 identified others, compared two American postulate theorists to European contemporaries, and analyzed their influence on mathematical logicians. I will undertake a broader review, attempting at least partial answers to the following questions: Who contributed to American Postulate Theory? What were the characteristics of their research? Who or what influenced them? Were there mutual influences or rivalries among them? What influence did they have on other lines of mathematical research? Did a theory of postulation develop?