Some of America’s earliest municipal pools and public baths had a purpose beyond recreation: keeping people clean.

In the late 1800s and early 1900s, many working-class families in rapidly growing cities lived in crowded tenements without bathtubs, showers or reliable access to hot running water. At the same time, growing acceptance of germ theory was changing attitudes toward sanitation and disease.

Public-health reformers responded by pushing cities to build public bathhouses where people could wash for free or very little. Some facilities also included communal pools, often called “plunge baths,” blurring the line between bathing and swimming.

But the movement wasn't only about germs. Progressive Era reformers often linked cleanliness with morality and “respectable” behavior, particularly among poor and immigrant communities. Public bathing was seen as a way to improve both public health and society itself.

As indoor plumbing became more common, the need for public baths declined. Municipal pools increasingly became places for swimming, exercise and recreation, and by the 1930s cities were constructing enormous public pools through New Deal programs.