A stacked bar chart visualizes quarterly sales contributions across four regions—South, Central, East, and West—from 2018 to 2021, with each bar segmented by region and colored via a categorical scale. The chart uses D3 v7 to load CSV data, compute stacked series through `d3.stack()`, and render SVG rectangles scaled by `d3.scaleBand()` and `d3.scaleLinear()`. Hovering over a segment reveals a tooltip with the exact sales value, while an external legend identifies each region’s color. Axes are drawn using `d3.axisBottom()` and `d3.axisLeft()`.