This interactive visualization displays demographic and income data for New Jersey, showing population counts or average incomes as scaled circles positioned by geographic coordinates on a county map. Users select which attribute to display via a dropdown menu, while a histogram below shows age distribution, with a d3.brushX selection filtering the map circles to show only data within the selected age range. The map uses d3.geoMercator projection with d3.geoPath to render county boundaries from TopoJSON, while circles are sized with d3.scaleSqrt based on the chosen metric, with data sourced from a CSV file containing individual income records.