The 1860 census reported 47 percent of Manhattan Island’s population to be foreign-born, as was 39 percent of Brooklyn’s. By comparison, just over 13 percent of the total U.S. population was foreign-born.

Until the 1850s, immigrants arriving in New York simply left the ships on which they had traveled, tied to piers lining the East and Hudson Rivers or anchored in the harbor, and joined the bustling cityscape. In an attempt to bring order out of chaos, the New York State legislature in 1847 established the Board of Commissioners of Immigration of the State of New York. In 1855, the commissioners secured the use of Castle Garden, originally built as a fort at the Battery to protect New York from attack from the sea. At Castle Garden, at the new Emigrant Landing Depot, officials guided the immigrants through a formal registration process and then worked with licensed boardinghouses and railroad agents to protect the new arrivals from the worst abuses.

During the period from 1855 through 1869, staggering numbers of immigrants arrived each year at Castle Garden. Even during the Civil War years, when immigration declined, hundreds arrived at the Battery each day. After the war ended, immigration resumed at a feverish pace—over two hundred thousand arrivals a year between 1867 and 1869.

Conditions for immigrants on the passage from Europe were often appalling. Shipowners crammed as many people as possible into the holds and provided them with rotting food and foul water. Many of the ships, especially the sailing ships long past their prime, became virtual death ships on which hundreds died on the voyage to the United States.