This thesis covers the history of American-Zanzibari commercial and diplomatic relations in the 19th and early 19th centuries, with a focus on the actions of the American consuls who served on the island from 1837 to 1915, when the consulate was moved to the mainland port city of Mombasa. Until 1895, all except two of the consuls were merchants, representing American commercial firms, and many of them came from the American city of Salem, Massachusetts, which shared a special economic connection to the island of Zanzibar. American merchants dominated Zanzibar's trade with Western countries until the American Civil War disrupted the production of cotton cloth, which formed the basis of their commercial success. The decades after the Civil War saw a decline in American commercial and political importance in Zanzibar. This thesis shows that the individual actions of the American Consuls in Zanzibar contributed to American commercial success in the region and shaped the course of Zanzibari and East African history, though not to the same extent as their European colonial counterparts. Additionally, the documentation provided by the American Consuls in Zanzibar provides a third-party perspective of the many changes that shook East Africa during the period of study. Keywords: Zanzibar; United States of America; East Africa; Trade; Diplomacy; 19th Century; Salem.