This visualization shows the evolution of U.S. historical tax rates for head-of-household filers from 1913 onward, with income thresholds adjusted to 2013-equivalent dollars. The chart displays marginal tax rate brackets as a function of income and year, sourced from Vox and the Tax Foundation. It uses D3.js to render the data, likely with scales and axes to map the JSON data’s year and income pairs. The rendering approach is visible in the code, which includes nested arrays of rate and threshold values per year.