Congress played a significant role in expanding rights to marginalized Americans during the 20th century. Here are a few examples.
1) 19th amendment- This constitutional amendment gave women in the United States the right to vote.
2) Civil Rights Act 1964- This law ended segregation in public places. This included movie theaters, restaurants, parks, etc.
3) Voting Rights Act of 1965- This law got rid of poll taxes, grandfather clauses, and literacy tests. During the late 19th and early 20th century, all of these were used as a means to prevent African-American citizens from voting. Thanks to the Voting Rights Act of 1965, all of these types of obstacles to stop African-Americans from voting were now illegal.
The purpose of the Marshall Plan was to aid in the economic recovery of nations after WWII and to reduce the influence of Communist parties within them.
I apologize if this is not what you meant.
