I learned recently that in 1951 – 1963, the top tax bracket was 91% (and 92% for two years)! That means every $1.00 over $400,000 was reduced to $.09!
So an additional $200,000 of income over $400,000 would be reduced to a measly $18,000.
It seems like that would be a very big incentive not to make money.
Update: As Les points out in the comments, this was a marginal tax bracket, so only the income over a certain level was taxed at that rate. I’ve changed the post to reflect this.