This multi-line chart displays state population trends from 1910 to 2010, with an interactive tooltip that appears when hovering over the chart. Built with D3 v4 and rendered as SVG, the visualization plots four states as colored lines (California, Texas, Michigan, and Elsewhere) and uses a vertical guide line to indicate the selected year. The tooltip lists all states sorted by their population for the hovered year, showing each state's name and population in its corresponding line color. Data is loaded from an external JSON file, and the tooltip updates dynamically as the mouse moves across the chart, with the nearest decennial year snapped to the data.