How Many Sides Does Colorado’s Border Really Have?

Congress may have drawn Colorado as a geospherical rectangle—closer to a trapezoid than a true box—but look closer and you’ll see it’s far from just a four-sided object.

Because of old surveys and a handful of court decisions, Colorado’s border isn’t a perfect shape at all. It’s actually a polygon stitched together from 697 straight-line segments. Keep reading to see how that happened—and why it stuck.

How Congress Imagined Colorado’s Borders

Congress tried to keep things simple by setting Colorado’s borders between 37°N and 41°N latitude, and 25°W to 32°W longitude. On maps and in textbooks, it looks like those lines were followed perfectly—but surveyors on the ground had a much tougher job.

Picture trekking through the Colorado wilderness in the late 1800s, tasked with driving stakes and stacking stones to mark the state’s edges across mountains, deserts, and wide-open plains. Armed with chains and star charts—but no satellites—the surveyors did the best they could. The outcome wasn’t four clean lines, but a patchwork of straight segments that gave Colorado far more sides than anyone expected.

The Surveyors’ Reality vs. Theory

Read More: The Surprising Story Of Colorado’s Lost Capital Contenders

Wait—there’s more. One quirky result of Colorado’s 697-sided border is that some landmarks aren’t exactly where you’d expect. Take the Four Corners Monument: the marker sits about 1,800 feet from the mathematically precise meeting point. Still, courts ruled the surveyor’s mark is the one that counts. Picture a map, like the one from FascinatingMaps.com, dotted with 697 points along Colorado’s edges.

Not long after statehood, mistakes along the southern border with New Mexico sparked lawsuits that climbed all the way to the U.S. Supreme Court. In 1925, the court ruled those “mistakes” were the official line—cementing Colorado as the first state with 697 sides. You can dive deeper into the many sides of Colorado at BigThink.com.

When Maps Don’t Match Reality

Once you know the truth, you never look at a map of Colorado the same way again. Our state’s tidy-looking rectangle is technically a polygon with 697 sides. Each side represents the straight lines created by humans, influenced as much by compromise as by math.

You could check our crooked southern border out for yourself by driving Highway 160 from the Four Corners to Kansas. Keep scrolling to check out ten places to stop along the way in the gallery below.

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