Got a link to this by chance?
2011:
>1.7 mill: 22.8%
>389,000: 23.5%
>168,000: 20.9%
120,000-168,000: 12.8%
70,500-120,000: 9.7%
34,800-70,500: 7.0%
$20,000 (1953) = $168,493 (2011)
$500,000 (1953) = $4,212,341 (2011)
$1,000,000 (1953) = $8,424,682 (2011)
So if you made $1,000,000 in real dollars over those "60" years. Your marginal rate has gone from 90% to 40%. Yet you've gone from paying only 46% to 24%.
EDIT: Some helpful and friendly jerk already made a graph for this apparently:

EDIT2: Was looking for "bottom" quintiles or something in a similar chart, will have to settle for bottom 90%

