What piece of legislation to expand the middle class

The Civil Rights Act

Explanation:

The Civil Rights Act of 1964 was a law that was passed in the United States which outlawed discrimination based on color, religion, sex, race or nationality. It also made it illegal to apply unequal voting registration requirements to different groups. Finally, it outlawed racial segregation. The legislation helped significantly expand the middle class by giving more equal and fairer opportunities to all people, and therefore encouraging their participation in society.

by improved communication.