Creating high density (1M+ Map Markers) map using a SHP file and Mapbox.com

styles.css

#YOUR_LAYER_ID {

  marker-opacity: 0.50; 
  image-filters: colorize-alpha(#00dfff, #00c9ff, #FFFFFF);
  
  marker-allow-overlap: true;
  marker-ignore-placement: true;
  marker-width: 2;
  
  [zoom < 15] {
    marker-width:  2;
  }
  [zoom >= 10] {
    marker-width:  4; 
  }
  [zoom >= 15] { 
    marker-width:  6; 
  }
  [zoom >= 16] { 
    marker-width:  8;
    marker-opacity: 0.75; 
  }
  [zoom >= 17] { 
    marker-width:  10;   
    marker-opacity: 0.75; 
  }
  [zoom >= 18] { 
    marker-width:  12;   
    marker-opacity: 0.75;
  }
  [zoom >= 19] { 
    marker-width:  16;  
    marker-opacity: 0.75; 
  }
  [zoom >= 20] { 
    marker-width: 24;   
    marker-opacity: 0.75; 
  }
  [zoom >= 21] { 
    marker-width: 32;  
    marker-opacity: 0.75;
  }
  [zoom >= 22] { 
    marker-width: 48;  
    marker-opacity: 0.75;  
  }

}

Tutorial

## Convert your SHP File to a GeoJSON File
1. Download and Unzip your SHP file
2. Change to the SHP file directory
3. Convert the SHP file to a GeoJSON file
````
ogr2ogr -f "GeoJSON" my_file.geojson my_file.shp
````

## Convert your GeoJSON File to Mapbox Vector Tiles
To convert a GeoJSON Feature Collection to a Mabpox Vector Tiles file, use Tippecanoe.

````
tippecanoe -o my_file.mbtiles my_file.geojson
````

Alternately you can adjust the density of the pins using the `-r` option, lower number for density (0) for no drop, higher for sparser (2+)