The geographic footprint of Boston has changed drastically over the past several hundred years. Luckily, there are many carefully drawn historical maps that have preserved the various stages of the changing landscape. In this map, I brought those historical coastlines back to life by overlaying them onto an interactive map of present day Boston.
To make this map, I first extracted the coastline geometry from the map images. I used maps from 1788 and 1898 from the Harvard Geospatial Library that are georeferenced and in GeoTIFF format. After uploading them as tilesets in Mapbox Studio, I used the maps as reference tilesets in the dataset editor and traced the coastlines by hand.
To highlight the changing coastlines, I did a figure-ground flip to the traced land and island polygons using Turf.js, so the map shows historical waters flowing over streets and places of today.
Use the dataset in a map
Next, I converted my historical coastlines dataset into a tileset using the dataset editor and added them to a custom style in Mapbox Studio. I then added the map legend and slideshow interactivity using Mapbox GL JS.