This is a simple setup of Leaflet (via Mapbox) with d3 to show dots on a map. This can serve as a base for many interesting geographically based visualizations
Nice overview of using d3 + Leaflet.
I found this slightly simpler to use than Mike's classic post.
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forked from enjalot's block: dots on a map: setup-gl
forked from enjalot's block: dots on a map-gl: circle