It only got a lot more equal because WW1, the Depression, and WW2 combined destroyed most of the stuff the rich people had.
Don't forget 92% marginal tax rates on income over $1 million/year.
That was slashed to 72% under JFK. But regional inequality only took took off after it was slashed to 50% then to 28% by Reagan.
Today the rich have lower tax rates than average Americans.