Answer:
The New Deal
Step-by-step explanation:
This is because the New Deal was one of the biggest policies of the 1900s and it is basically the biggest step we took to take ourselves out of the great depression, aswell as Social security being a major part of the new deal and Roosevelts following policies. Plus, it can't be the great society or NASA becasue both of these were created many decades by other presidents, the great society being created by LBJ and NASA being founded by Dwight D. Eisenhower the president before JFK who mainly utilized NASA to help lead the US into the 21st century with its many advencements of technology and space travel.