The 16th Amendment to the United States Constitution, ratified in 1913, allows Congress to levy an income tax without apportioning it among the states based on population. This amendment was significant because it provided the federal government with a steady source of revenue to fund various programs and services. Before the 16th Amendment, income taxes were often seen as unconstitutional or unfair. The amendment clarified the government's ability to tax individual earnings, leading to the modern income tax system that is still in place today. This change has had a lasting impact on the U.S. economy and fiscal policy.