This is a large part of the story of rising US income inequality.
The major changes to the rates were as follows:
(1) from 1933 to the early 1940s the top marginal tax rate was progressively increased from about 60% to about 90% to fund the war effort, and stayed at 90% until the Kennedy–Johnson tax cut of 1964.
(2) the Kennedy–Johnson tax cut of 1964 reduced it to 70%.
(3) then under Reagan’s presidency the top marginal tax rate on ordinary income was reduced to 50% in the Economic Recovery Tax Act of 1981 and to 30% in 1988.
(4) subsequent changes have been minor, and the rate has fluctuated in a range from 30 to 40%.
