In case you're not sure what is included in the 20th century...
-Social Security, Medicare, Unemployment
-The FDIC
-Desegregation and Brown vs. Board
-LGTBQ Rights
-The 19th Fucking Amendment
-Civil Rights Act and Voting Rights Act
-Clean Air and Clean Water Acts
-Freedom of Information Act
-Presidential Records Act
-War Powers Act
There's probably so much more genuinely important shit that serves Americans and reigns in governmental/presidential power that I'm missing