Dustin Cable suspected the online map he built to plot the distribution of the entire U.S. population by race—a color-coded dot for all 308.7 million Americans identified by the 2010 Census—would be interesting, useful, and maybe even important.

He didn’t think it would be so beautiful.

“I didn’t expect, for instance, the blending of colors at the different zoom levels,” said Cable, senior policy researcher and statistician for the Demographics & Workforce Group at UVA’s Weldon Cooper Center for Public Service. In views of cities across the map, smudges of mixed shades give way to a vibrant array of dots at the neighborhood level. “Some commenters in the blogosphere are calling it demographic pointillism,” Cable said.

Also unexpected: The level of interest the map generated when the Cooper Center launched it earlier this month. It was quickly picked up by blogs around the country, and spent a day as the top story on Slate. “We’ve actually crashed a couple of servers,” Cable said.

The idea for the map grew out of a similar project created by Brandon Martin-Anderson of the MIT Media Lab, who used census data to create a population density map of North America last year. The zoomable black-and-white image got Cable thinking: What about the rest of the information in the Census?

He built on Martin-Anderson’s open-source code, layering in data for race and ethnicity, and used software plotted respondents by Census block—a geographic unit about the size of a standard city block. “What you’re seeing is a combination of 1.2 million individual image files,” Cable said. “As you zoom in and out, it’s creating new images.”

Each dot—blue for white, green for black, orange for Hispanic, red for Asian, brown for other—is smaller than a pixel at most screen resolutions, he explained, which is what leads to the striking color blends at high zoom levels.

Zero in on a city, however, and the map often reveals stark and sometimes surprising patterns of racial segregation. In Charlottesville, 10th Street Northwest shows up as a dividing line between mostly white Corner blocks and the almost all-black 10th and Page neighborhood, and the highest concentration of Asians surround UVA’s Darden School and medical center.

Commenters in the blogosphere have noted some other fascinating details. Many wondered about what Cable called “stark little green boxes” showing up in largely rural areas, including Fluvanna County.

“Once you dig further and look at the addresses, you’ll see they’re correctional facilities,” he said.

But what Cable is more interested in are the bigger conversations he hopes the map will spark.

“People are discussing what segregation means, whether it’s self-selective, or whether it’s part of a deeper racial tension in some of these areas,” he said. “I’m already starting to see that.”