Final answer:
Immigrants often lived in crowded and rundown tenements in ethnic slums, which posed health risks and spread diseases.
Step-by-step explanation:
The immigrants often lived in ethnic slums in crowded buildings called tenements. These tenements were rundown and crowded, with multiple families crammed into small apartments. Lack of fire protection and sanitation in these slums posed serious health risks, leading to the spread of diseases such as tuberculosis and pneumonia. Immigrants formed ethnic communities within these slums, such as Little Italy or Chinatown, where they could find familiar language, culture, and support.