This visualization displays the population of various states over time using an interactive line chart. The chart, rendered as an SVG with D3 v4, plots year on the x-axis and population on the y-axis. Hovering over the chart triggers a tooltip that ranks states by their population for that specific decade, with a vertical line marking the selected year. The code uses `d3.line`, `d3.axisBottom`, and `d3.axisLeft` to generate the chart, and it loads data from a CSV file hosted on GitHub Gist.