The first income tax was very low.
It was only 1% of your income.
And it only taxed rich people who made over $3,000.
Adjusted for inflation a person making $3,000 in 1913 would be failry well off today and make $57,000 in 2004 dollars.
If you made over $20,000 the income tax double from 1% to 2% on the income over $3,000.
The maximun income tax rate was 7 percent for taxpayers with income in excess of $500,000.
Less than 1 percent of the population paid income tax at the time.
Here are some income tax forms from 1913.
Read them and weep.