This thesis examines the process by which General Motors' Cadillac brand of automobiles came to dominate the U.S. luxury car market between 1927 and 1960. In 1927, Cadillac was only one among a crowded field of U.S. and European automobiles priced above $3000, the threshold of the luxury car market at the time. Through a skillful process of marketing, the corporate strength of General Motors, and the mistakes and ill-fortune of its competitors; Cadillac came to hold at least 50% of the U.S. luxury car market throughout the 1950s, and in some years accounted for nearly 70% of that market. It also briefly examines the reasons for Cadillac's decline in the market during the years since 1960.