Ward 8, where Marion C. Barry campaigned for a D.C. Council seat in this weeks election, is 94 percent non-Hispanic black.s election, is 94 percent non-Hispanic black.

Vince Gray may have repeated his “One City” mantra a thousand times during his tenure as mayor, but this city remains among the most segregated in America.

Data guru Nate Silver has crunched the numbers on racial diversity in the country’s 100 biggest cities, and he’s broken them down in a novel and important way, plotting overall city diversity against neighborhood diversity. Some cities, like Chicago, are very racially diverse, but the races are clustered in certain sections of town, with little mixing. Others, like Portland, Ore., have reasonably diverse neighborhoods given their overall demographics, but lack enough racial diversity citywide for it to mean all that much.

Silver compiled an “Integration/Segregation Index,” which measures how far a city’s diversity in its individual census tracts strays from its overall diversity. Irvine and Sacramento, Calif., come out on top, with neighborhoods that are nearly as diverse as the cities themselves. Chicago is in dead last, with highly segregated neighborhoods.

And D.C.? The nation’s capital is its sixth most segregated city.

Even with increased racial mixing in certain areas near the center of the city, D.C. remains wildly segregated, with an overwhelming white majority west of Rock Creek Park and an overwhelming black majority east of the Anacostia River. Overall, the city is slightly more diverse than the average big city in America: Of the country’s 100 largest cities by population, D.C. is the 46th most diverse. But its census tracts are the 22nd least diverse in the country. Put those numbers together, and you have one of the most segregated cities in America.

D.C.’s racial divide is evident to anyone who’s spent time in the city. It shows up in every facet of District life, including voting patterns, home purchases, and school choice. And much as the city’s political leaders may pay lip service to increasing unity, there’s not much evidence that it’s actually happening.

For more details and methodology, check out Silver’s analysis.

Photo by Darrow Montgomery