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For those who live in big urban areas, subway systems offer a familiar and powerful frame of reference for understanding variations across a city. That’s why cartographers and data scientists have started using the subway systems of New York, London and other major cities as an innovative way to map and visualize urban data.

Now MIT’s You Are Here project has done the same for Washington D.C., creating this visualization of median household incomes by station along the city's Metro system. The graphic draws on census data on earnings within a radius of half a mile around subway stations. It graphs both the median household income for each stop and the overall average for the line.

The line with the highest income overall is the Orange Line, with an average median household income of $97,236.

That’s closely followed by Silver Line with $92,205, the Red Line (pictured above) with $91,921, and the Blue Line with $91,174.

Looking at the graphs, you can see that these higher average incomes result because of a sharp discrepancy in income between Washington’s eastern and western halves. These “wealthier” lines all run into the richer Western suburbs, bringing up the average for the whole line.

The Orange Line, pictured above, runs into wealthier suburbs like Falls Church, VA, which pull up the overall average. In the east, the station runs through some poorer neighborhoods, including the station with the lowest median household income in Washington -- Minnesota Avenue, at $33,947.

In contrast, the Yellow Line runs down the center of Washington, while the Green Line runs only through the less wealthy eastern quadrants – which is the reason that the Green Line’s average income is much lower than the rest, at $65,619.

The full interactive version, visible here, lets you flip between lines and look at income data for each metro stop. This is the first project from You Are Here’s new open-source library, which allows census data for any city to be visualized over a transit network.