The reason for Baltimore’s emergence as the leading centre of the mackerel industry towards the end of the 19th century and the accompanying prosperity – after more than two centuries of social obscurity and economic stagnation – are explored in this work. Baltimore’s importance as a landing place for mackerel was primarily dependent on non-local fishermen with superior catching power. English fish buyers dominated the marketing and distribution of fresh mackerel to England and cured mackerel to America in the absence of a viable home market. However, the arrival in 1879 of Fr. Davis in Baltimore as parish priest and his collaboration with English philanthropist Baroness Burdett-Coutts, enabled Baltimore to capitalize on the new opportunities afforded by fortuitous changes in the mackerel industry. Despite the short term nature of the economic success of Baltimore as a centre of the mackerel industry, the author shows how this industry created a cosmopolitan blend of people and saw the development of its marine infrastructure and onshore services.