This interactive D3.js bar chart visualizes FBI NICS background check data across U.S. states, showing stacked totals for handguns, long guns, other firearms, and multiple gun purchases. Users can select the year, filter to top states, and sort by value or alphabetically. Bars transition smoothly between states using D3 transitions, with a legend that highlights categories on hover and tooltips revealing per-category counts. The visualization updates automatically through an animated playback mode.