This thesis covers the history of coast defenses in the territory of the United States from the time the Spanish built the first coastal fort at St. Augustine, Florida in 1565 to the inactivation of the Coast Artillery Corps in 1950-marking an end to the long era of fixed coast defenses. Special emphasis, however, is placed on the completion of a modern coast defense system, featuring expensive, large-caliber, high-power guns in concrete/ earth emplacements, during the period from 1885 to 1915. The paper is organized into a preface, six chapters and an appendix. The preface covers first the overall cost of the highly expensive modern system, and points out that it was practically never required for combat operations. This is followed by an explanation of the assumptions and traditions that caused the nation's leaders to place their faith in coastal fortifications with their permanently emplaced guns up to the late nineteenth and early twentieth century. Chapter I covers the history of coast defenses from the time of the first permanent settlements in the area of the United States through the Revolutionary War and the War of 1812. It explains why the earliest colonists built coastal forts almost as soon as they built their homes, and it outlines the the role that the forts of colonial times played in the wars of that period. It portrays the overall weakness of the coastal fortifications in the Revolutionary War as well as the War of 1812, although the new republic had spent a substantial amount of money and exerted considerable effort to build an effective coast defense system from 1794 to 1812. [...]