Denver’s nickname, the “Mile High City,” is due to a quirk of topography.

Although most of downtown Denver is situated just below 5,280 feet in elevation, the adjacent Capitol Hill district sits on a slightly higher knoll. As a result, the historic Capitol, with its glistening, 24-karat-gold-leaf dome (first added in 1908), surpasses this datum, thereby granting Denver its notable claim to mile-high fame.

But exactly which step in front of the building marks one-mile high? There are, in fact, three markers embedded in the white granite steps on the western side of the Capitol. Most obvious are the words “ONE MILE ABOVE SEA LEVEL,” which are carved into the riser of the 15th step, counting from the bottom. This phrase was inscribed in the native Colorado rock in 1947 after several plaques, including the very first mile-high marker, placed in 1909, had been stolen.

In 1969 a new brass benchmark was placed on the 18th step after several Colorado State University engineering students resurveyed the elevation and concluded that the inscription and original marker had been placed three steps too low. This changed yet again in 2003, when even more accurate measurements determined that the second marker had been placed 3.03 feet too high. On September 29, then-Governor Bill Owens presided over a ceremony during which a new brass benchmark depicting the Rocky Mountains was affixed, this time to the 13th step.

Just how long number thirteen stays the lucky step, however, remains to be seen.

Visit: While you can visit the mile-high step(s) at any time, if you’d also like to explore the inside of the Capitol, the building is open to the public on weekdays from 7:30 a.m. to 5:00 p.m. To get more out of your visit, consider signing up in advance for a free tour, especially if your group exceeds 10 people. These are offered hourly on weekdays from 10:00 a.m. to 3:00 p.m. (Tours are offered every half-hour during June and July.) The Capitol Building is located at 200 E. Colfax Ave., on the eastern side of Denver’s Civic Center Park.

(See more from 5280‘s Only in Colorado series)

Terri Cook
Terri Cook
Terri Cook is an award-winning freelance writer based in Boulder. More of her work can be found at down2earthscience.com.