Nelson Minar didn’t really mean to create a piece of art. When the California-based software engineer began working on All Rivers, a gorgeously detailed look at the waterways in the 48 contiguous states, it was really just a practice in computer nerdery. Minar, a self-described “computer nerd at heart,” simply wanted to create a vector map (a map consisting of Geographic Information System data) using open source data. “The single All Rivers map was just me goofing around to see what it’d look like,” he told Wired.

It looks pretty cool. Inspired by Ben Fry’s All Streets poster, Minar’s version shows a vast web of blue veins spreading across the United States. River-rich areas like Mississippi are dense with blue, but more surprisingly, so are notoriously dry areas like Nevada and Arizona.

To create All Rivers, first Minar gathered information from NHDPlus (National Hydrography Dataset) and put it in a database. He extracted the Strahler number, a measure of how significant a creek is, to determine how large the rivers would appear on the map. From there he built a web server that would allow him to serve the flowline data as vector map tiles, and finally he wrote a JavaScript program that did most of the cartography work for him.

Minar kept All Rivers pretty simple, using only the Strahler number as a variable. But he says it’s possible to gather more information to include on future maps. “To be a useful hydrography map, it should have information on river volume, size, seasonality, etc,” he said. “That’s a lot of data to cram into a single picture. I don’t know how to do that and make it look good.”