This choropleth map displays the percentage of adults age 25 and older with a bachelor’s degree or higher across U.S. counties, using data from the FreeCodeCamp education dataset. Counties are colored with a threshold scale using `d3.schemePurples[8]`, with missing data rendered in gray. The map is built with React and D3 v5, using `d3.geoPath` to project county boundaries from TopoJSON, while a custom legend and hover tooltip show exact percentages. The tooltip positioning and visibility are handled manually through mouse events.