Add a GeoJSON polygon
Style a polygon with the fill layer type
<!DOCTYPE html>
<html>
<head>
    <meta charset='utf-8' />
    <title></title>
    <meta name='viewport' content='initial-scale=1,maximum-scale=1,user-scalable=no' />
    <script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.39.1/mapbox-gl.js'></script>
    <link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.39.1/mapbox-gl.css' rel='stylesheet' />
    <style>
        body { margin:0; padding:0; }
        #map { position:absolute; top:0; bottom:0; width:100%; }
    </style>
</head>
<body>

<div id='map'></div>
<script>
mapboxgl.accessToken = '<your access token here>';
var map = new mapboxgl.Map({
    container: 'map',
    style: 'mapbox://styles/mapbox/streets-v9',
    center: [-68.13734351262877, 45.137451890638886],
    zoom: 5
});

map.on('load', function () {

    map.addLayer({
        'id': 'maine',
        'type': 'fill',
        'source': {
            'type': 'geojson',
            'data': {
                'type': 'Feature',
                'geometry': {
                    'type': 'Polygon',
                    'coordinates': [[[-67.13734351262877, 45.137451890638886],
                        [-66.96466, 44.8097],
                        [-68.03252, 44.3252],
                        [-69.06, 43.98],
                        [-70.11617, 43.68405],
                        [-70.64573401557249, 43.090083319667144],
                        [-70.75102474636725, 43.08003225358635],
                        [-70.79761105007827, 43.21973948828747],
                        [-70.98176001655037, 43.36789581966826],
                        [-70.94416541205806, 43.46633942318431],
                        [-71.08482, 45.3052400000002],
                        [-70.6600225491012, 45.46022288673396],
                        [-70.30495378282376, 45.914794623389355],
                        [-70.00014034695016, 46.69317088478567],
                        [-69.23708614772835, 47.44777598732787],
                        [-68.90478084987546, 47.184794623394396],
                        [-68.23430497910454, 47.35462921812177],
                        [-67.79035274928509, 47.066248887716995],
                        [-67.79141211614706, 45.702585354182816],
                        [-67.13734351262877, 45.137451890638886]]]
                }
            }
        },
        'layout': {},
        'paint': {
            'fill-color': '#088',
            'fill-opacity': 0.8
        }
    });
});
</script>

</body>
</html>
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