Although Native Americans were using their geological knowledge to operate a chert quarry 13,000 years ago in northeastern Colorado and others were harvesting paint pigments near Calhan for many centuries; the first recorded geological observations were made early in the 19th Century.
On his expedition into the San Luis Valley in 1821-22, Jacob Fowler recognized the geological evidence indicating that a large lake 40 to 50 miles wide and about 200 feet deep existed in the distant geological past. This phenomenon was not documented and confirmed until the first decade of the 21st Century.
Many noted geologists worked in Colorado in the latter half of the 19th Century.
The King Survey of the 40th Parallel made the first regional geologic map in Colorado during the latter years of its expedition which ran from 1867 to 1872. The chief geologists for the survey were S. F. Emmons and Arnold Hague who worked directly under Clarence King, later appointed the first Director of the US Geological Survey.
John Wesley Powell made a survey of Middle Park in 1868 and accomplished the first recorded ascent of Longs Peak (14,259' AMSL) in Rocky Mountain National Park that same year.
In 1869, F. V. Hayden conducted the first of a series of expeditions to explore the geology of Colorado and Wyoming. The Hayden survey published the first Geologic Atlas of Colorado in 1877
. This contained not only a statewide map, but more detailed geologic maps on a topographic base at 1:253,440 scale.