Maps can tell us all kinds of things about how others have viewed and shaped the world – from the borders of ancient empires to the layout of your neighborhood street grid. Today, spatial data commonly powers the maps and applications we use to access basic information about the places we inhabit: opening an app on your phone can quickly help you locate a nearby restaurant or estimate the value of your home. Cities also use spatial data to manage and inventory public works, and often times this data is made open and freely available for public use.
Here in Washington, DC, the DC Government utilizes an open data site to host spatial data files that document everything from the location of street lights to street trees. These data files are routinely updated and often contain quite a bit of detailed information.
Today’s use of open data to document the city is not a new phenomena: before this data was downloadable with the click of a button, it still existed, just in a different form. Terrific examples of this include the City of Washington’s Statistical Maps of 1880 and 1891 Maps of the DC Engineering Department, both held in the Geography & Map Division. Both sets of maps allow us to peer back nearly 150 years in time to see what our neighborhoods looked like then and how things have changed (and not changed) over time.
A great example is this 1880 Street Pavement map of the City of Washington, which uses color to differentiate between different methods of street paving.The edges of the city remain “unimproved,” while many of the downtown streets, including around the White House and Capitol, are made of asphalt or concrete. 16th Street NW, today a major north-south thoroughfare through the city, was paved with wood – as were major sections of New Jersey Avenue. The map’s legend also documents the total length (in miles) of maintained roads within the city of each type of paving. Unimproved roads accounted for over 41% of the city’s roads at the time.
Another map from 1894 details Washington’s underground cable infrastructure:Underground cables included cables from the U.S. Electric Lighting Company, the Chesapeake and Potomac Telegraph Company, Western Union Telegraph, Postal cables, and U.S. Government and District municipal cables. This detailed look at the area around the White House shows the greatest concentration of underground cables in the city, with telegraph, electric lighting, and U.S. Government cables all connecting to the executive grounds out into the surrounding streets.
As a final offering, the map below shows the location of gas lamps (used as street lights) in 1880, which quickly distinguishes the city’s main thoroughfares from smaller side streets. At the time this map was produced, electric street lights had just made their first-ever debut in 1879 on Cleveland city streets.These historic maps can be combined with today’s spatial data to create visualizations that show the difference in placement and quantity of today’s street lights with the gas street lamps of the past. The above visualization provides a detailed look at DC’s Judiciary Square with 2022 Street Light data from DC Open Data layered on top of the original 1880 gas street light map. The proliferation of street lighting over the last century is quickly made visible.
Today’s spatial datasets contain more information than was possible a century ago: data detailing the number of lights and arms on each street lamp, the height of the pole, and even the wattage of the electric lights are all stored in the file’s attribute table. Practical municipal maintenance information is included also, such as the composition of each light pole, the date it was last painted, and the make and model of lightbulbs. This detailed information allows us to create a variety of different possible cartographic visualizations. On the right, you can see a quick visual illustration of Judiciary Square street lighting in 2022, using the wattage of each street light to dictate symbol size. While today’s data may give us more cartographic options, it also presents new and interesting challenges to think through about how to best capture and preserve spatial data, so DC residents in 2164 can look back and see how much has changed about their city streets (and perhaps, how much remains the same!).