Four county-level COVID-19 case counts appear as smooth, colored line charts over time, with a categorical color legend identifying each county. The visualization uses D3 v5 with an SVG renderer, nesting the CSV data by county and drawing paths with `d3.line` and `curveBasis`. Axes are generated via `d3.axisBottom` and `d3.axisLeft`, while a custom `colorLegend` function renders the ordinal scale.