This interactive tree visualization displays the hierarchical structure of US states and their counties, organized under eastern and western regions. Using D3.js v7 with the `d3.tree` layout, nodes are rendered as circles with colored links distinguishing between regions, states, counties, and cities. The SVG rendering applies distinct stroke colors for each hierarchical level—red for regional links, blue for state links, and green for county links. The static dataset defines six states across two regions, with counties and one city as leaf nodes, presented on a light blue background with labeled node text.