In the late 1840s, a plant disease called blight ruined Ireland’s potato crop. Potatoes were the main food for millions of people. Hunger and disease spread. More than a million died, and more than a million left. Between 1845 and 1855, about 1.5 million Irish sailed for North America. Many arrived weak and poor after long, unsafe voyages on “coffin ships.” Most did not head for farms. They stayed in the port cities where their ships landed.
This wave of immigration sped up urbanization in the United States. New York, Boston, and other ports gained people quickly. In 1847, about 52,000 Irish reached New York, and by 1855, about one out of every four people in Manhattan was Irish. By 1850, the nation counted nearly a million residents of Irish origin, and the Irish made up the largest share of the foreign-born. Crowded neighborhoods of tenement houses spread near docks and workplaces.
Irish newcomers changed city life. Men loaded ships, dug canals, built roads, and labored on rail lines and construction crews. Women worked as domestic servants. They also labored in textiles and other workshops. Their pay was low, yet their efforts helped expand factories and markets. With more workers, cities added more shops, carters, and street sellers. Parishes, markets, and boardinghouses grew up around Irish streets, adding new sounds, foods, and faith traditions to the city.
Rapid growth strained services. Tenement houses often lacked clean water and sewers. Cellars flooded, trash piled up, and diseases such as cholera spread. City leaders had a hard time providing enough police, fire protection, and public works. Many employers welcomed the larger workforce. Others posted “No Irish Need Apply,” and some landlords divided old homes into small, cramped rooms to rent at high prices.
Not every Irish migrant stayed in the first landing place, but most remained in cities. Their numbers shifted the balance between rural and urban life. By filling city jobs and forming new communities, famine immigrants made American cities larger, denser, and more diverse before the Civil War era.