Final answer:
The most important piece of legislation fostering equal opportunity in the United States was the Civil Rights Act of 1964. It banned discrimination based on race, color, religion, or national origin in employment practices and public accommodations.
Step-by-step explanation:
The most important piece of legislation passed by Congress fostering equal opportunity in the United States was the Civil Rights Act of 1964.
The Civil Rights Act of 1964 banned discrimination based on race, color, religion, or national origin in employment practices and public accommodations. It ended racial segregation in schools, workplace, and public facilities.
Additionally, the act established the Equal Employment Opportunity Commission (EEOC) to monitor employment discrimination claims and enforce the law.