October 3, 1913:

President Woodrow Wilson signed into law the Revenue Act of 1913, a landmark piece of legislation that fundamentally changed how the U.S. government would collect revenue. This act was introduced in response to the ratification of the 16th Amendment, which gave Congress the power to impose an income tax without apportioning it among the states based on population. 

The act established a progressive tax system where individuals with incomes over $3,000 (equivalent to approximately $95,656 in today's dollars) would pay a rate of 1%, with the tax rate increasing up to 7% for incomes above $500,000. For married couples, the threshold was set at $4,000. This was a significant shift from previous taxation methods, offering exemptions for incomes below these thresholds, adjusted for marital status.