This visualization shows Grand Rapids, Michigan ZIP codes as choropleth-style regions, with population density encoded through fill opacity and color intensity. The map uses a customized azimuthal equal-area projection via `d3.geoPath` and `geoAzimuthalEqualArea`, rotated to focus on the city. ZIP code boundaries render from a GeoJSON source, while population data from city-data.com drives a `scaleLinear` mapping to opacity. Hover tooltips display each ZIP code and its population, and the map includes Michigan administrative outlines for context. React manages component state, with D3 v6 handling data loading and path generation.