A choropleth map of 23 Massachusetts South Shore towns displays population trends from 2000 to 2023 using a year slider and a diverging red-yellow-green color scale for annual percent change. d3.geoPath and d3.geoMercator render simplified town boundary polygons from a GeoJSON file, while React manages the slider state and window resizing. Clicking any town opens a line chart showing its population over time, and interactive hover highlighting links map features with their legend entries. All population data is loaded from CSV files via d3.csv.