People began to realize Denver’s elevation was exactly one mile (5,280 feet) in stages, starting in the late 1850s and becoming more precise and culturally recognized by the early 20th century.
In the earliest settlement period of the 1850s, pioneers had a basic sense of elevation. Barometers arrived in the region around 1859, and settlers used them to estimate elevation with reasonable accuracy. Early measurements placed Denver’s elevation near 5,200 feet, just shy of a full mile above sea level. These readings reflected general knowledge rather than pinpoint accuracy.
By 1869, the Ferdinand V. Hayden Survey conducted a detailed scientific evaluation of the Denver area. Using triangulation, theodolites, and precise baseline measurements, the survey cataloged reference elevations for Denver and its surroundings. While this improved accuracy, it did not clearly establish the exact spot of one-mile elevation within the city.
In 1871, the U.S. Army Signal Corps set up the first official weather station in downtown Denver at the corner of Larimer and G Streets (present-day 16th Street). Using barometric data paired with additional surveying, they determined the station’s site to be at 5,193 feet, confirming previous approximations but still below exactly one mile.
The key change came in 1874 when Denver expanded its city limits by annexing surrounding land, including Capitol Hill. This annexation incorporated terrain reaching 5,280 feet—a full mile in elevation—into the city’s official boundaries. Prior to this, original Denver lay entirely below that mark.
Although Denver was known to lie roughly a mile high by the 1870s, the exact definition of where “one mile” was located shifted over the ensuing decades. The Colorado State Capitol building, constructed in the late 19th century, became a focal point. A bronze or stone plaque marking 5,280 feet was embedded into the Capitol stairs, originally placed on the 15th step in 1909.
However, advances in surveying technology and updates to geodetic datum (the baseline measurements for sea level) caused this marker’s position to be revised. In 1969, it was found that the 15th step was not exactly at 5,280 feet. The marker was moved to the 19th step to reflect a more precise elevation.
A subsequent 2003 survey refined the elevation measurement even further, repositioning the official marker on the 13th step of the Capitol stairs, demonstrating ongoing improvements in measurement precision.
Culturally, the “Mile High City” nickname appeared gradually after Denver’s founding in 1858. The earliest recorded use of “Mile High” in Denver-related names dates to 1889 with a local temperance group. The broader usage of “Mile High City” came into common currency in the early 1900s, mentioned in newspapers by 1907 and becoming widespread by 1910. This nickname celebrated Denver’s unique geographical trait and helped define its identity nationwide.
| Year | Event | Elevation Knowledge |
|---|---|---|
| 1859 | Barometer-based measurements | Approx. 5,200 feet, early awareness of elevation |
| 1869 | Ferdinand V. Hayden Survey | Scientific baseline for elevations near Denver |
| 1871 | Army Signal Corps Station | Official measurement at 5,193 feet downtown |
| 1874 | Annexation of Capitol Hill | Denver gains land at or above 5,280 feet |
| 1889–1910 | “Mile High” term gains popularity | Begins cultural identity as Mile High City |
| 1909 | First Mile High marker on Capitol stairs | Mark placed on 15th stair step |
| 1969 | Elevation data update | Marker moved to 19th step due to accuracy |
| 2003 | Latest survey adjustment | Marker positioned on 13th step |
This timeline shows that while approximate elevation was known in the 19th century, the precise claim of Denver being “one mile above sea level” evolved with expanding city boundaries and advancing measurement techniques. The popular nickname and official markers followed later, reflecting both science and civic pride.
- Early settlers had elevation data by 1859, but only approximate.
- Scientific surveys in 1869 and 1871 improved accuracy without definitive mile-high designation within original limits.
- Denver’s 1874 annexation incorporated land at or above 5,280 feet, introducing official mile-high elevation.
- The “Mile High City” nickname appeared by late 19th/early 20th century, gaining popularity by 1910.
- Official elevation markers moved several times on Capitol stairs as measurements refined (1909, 1969, 2003).
When did people first have an idea of Denver’s elevation?
By 1859, early settlers used barometers to estimate Denver’s elevation around 5200 feet. They understood the area was high but had not pinpointed the exact mile mark.
When did Denver actually include land at one mile elevation?
Denver did not have any land at or above 5280 feet until 1874. That year, the city expanded to include Capitol Hill, reaching the mile-high mark.
How accurate were the early elevation measurements?
Early measurements from 1859 to 1871 used barometers and trigonometry. Accuracy improved over time, but exact locations of the 5280-foot point shifted with updated surveys.
Why do markers for Denver’s “one mile” elevation change locations?
Changes in sea level definitions, measurement tools, and standards altered where “5280 feet” is marked. Surveys in 1909, 1969, and 2003 placed the mile-high marker on different steps of the State Capitol stairs.
When did Denver adopt the “Mile High City” nickname?
The term appeared by 1889 in local groups. By 1907, “mile high” was used in newspapers, and by 1909 it became capitalized, showing the city’s identity embraced the elevation fact.
