Progressivism was a political movement that

Progressivism was a political movement that supported social reform.

Explanation:

This was a movement which rose to its peak popularity in the early 20th century, and its ideals mainly surrounded the changes already taking place due to modernization. New problems which had never been faced before began once the industrialization of the United States occurred, such as issues surrounding immigrants, low-skill factory workers and the displacement of small scale manufacturing with massive manufacturing plants, new inventions which increased production that quickly led to a need of the old reforms to be rethought in order to set a standard which applied in a more valuable way to the current times.