Thurman Arnold (1891-1969) was a major iconoclast of American law and a great liberal of the 20th century. In this first biography of Arnold, Spencer Weber Waller traces Arnold's life from his birth in Laramie, Wyoming, and explores how his western upbringing influenced his distinctive views about law and power. After studying at Princeton and Harvard Law School, Arnold practiced law in Chicago, served in World War I, and eventually returned to Laramie, where he was a prominent practitioner, mayor, and state legislator in the 1920s. As the rise of national corporations began to destroy the local businesses that were the core of his legal practice, Arnold turned from the courtroom to the academy, most notably at Yale Law School, where he became one of the leading spokesmen for the legal realism movement. Arnold's work attracted the attention of Franklin Roosevelt, who appointed him to head the Antitrust Division during the New Deal. He went on to establish Arnold, Fortas & Porter, which became the epitome of the modern Washington, DC law firm, and defended pro-bono hundreds of clients accused of Communist sympathies during the McCarthy era. One of the few individuals who shaped 20th century American law in so many of its facets, Arnold's biography is long overdue, and Waller honors his life and legacy with a book that is both vividly narrated and extensively researched.