A grid of color-coded squares displays the population of eight Massachusetts South Shore towns for a selected year, with each square showing the population, annual percent change, and town name. The fill color maps from red to green based on percent change, using the D3 `interpolateRdYlGn` color scale with a legend. A slider updates the displayed year, re-rendering the visualization with data from CSV files loaded via D3's `csv` module, and the React app manages the state.