This visualization displays a map of crude oil pipelines across the United States, with each pipeline colored according to its operating company. The map shows state boundaries, city labels, and pipeline routes, with a panel that displays the pipeline name and operator on mouseover. The code uses D3.js v4 with `d3.geoPath`, `d3.geoAlbersUsa`, and `topojson` to render the map, reading geographic data from a TopoJSON file containing both pipeline and state/city features. Pipeline colors are mapped to operator names, and hovering highlights the selected pipeline while dimming others. The data originates from the U.S. Energy Information Administration’s pipeline shapefiles and Atlas-Make for states and cities.