Alexander Rapp created a set of diagrams for subway systems around the world. Each shows the system’s geographic layout, all to the same scale, at various points in time. You can step forward and backward throughout history and see how, and when, each one evolved.

Washington

2010 map Boston

2010 map Chicago

2010 map

Click here or press the ‘a’ key to move all of the maps back five years. Click here or press ‘s’ to move ahead five.

New York

2010 map London

2010 map

Rapp chose which lines to show in each city by where there is frequent midday service, significant grade-separated areas, and closely-spaced stops (to exclude commuter rail) as of the end of the listed year. (Here’s more on his methodology).

His maps are 10 pixels per kilometer; I’ve selected a representative set of cities and shrunk Rapp’s maps to half their original size (5 px/km) so you can see more of them at once. You can look at the full size versions and all of the cities here.

Madrid

2010 map Paris

2010 map Moskva

2010 map

Some of the maps aren’t available for all dates. The ones below don’t have maps for years ending in 5 at all, or only have them after some date.

Beijing

2010 map Guangzhou

2010 map

México

2010 map São Paulo

2010 map Mumbai

2010 map

What do you notice on the maps?

David Alpert created Greater Greater Washington in 2008 and was its executive director until 2020. He formerly worked in tech and has lived in the Boston, San Francisco Bay, and New York metro areas in addition to Washington, DC. He lives with his wife and two children in Dupont Circle.