Colorado State Dinosaur: Stegosaurus

The Morrison Formation is a sequence of Late Jurassic sedimentary rock that stretches across 13 states in the American West. It is named after the town of Morrison, Colorado, where geologist Arthur Lakes first collected dinosaur bones in 1877. This naming is not incidental: the Morrison Formation is the single most productive source of Late Jurassic dinosaur material in the world, and its name carries a Colorado address.

Colorado sites within the Morrison Formation have produced Stegosaurus, Allosaurus, Diplodocus, Camarasaurus, Brachiosaurus, and dozens of other taxa. The two most historically productive Colorado localities are Garden Park, near Cañon City, and the Morrison area itself near Denver. Both were active in the 1870s and 1880s, during the period of intense competition between paleontologists Othniel Charles Marsh and Edward Drinker Cope — the era now called the 'Bone Wars.'

When Marsh named Stegosaurus in 1877 based on Colorado material, he was working in a period of frantic collection and rapid-fire publication. Specimens from multiple Colorado localities contributed to his understanding of the animal — and also to his confusion. Marsh initially thought Stegosaurus was aquatic and placed its plates flat along the back. The correct upright plate arrangement took years to establish.

The Garden Park area near Cañon City, Colorado, was one of the most contested fossil sites of the Bone Wars era. Marsh and Cope both had collecting teams working the area in the 1870s and 1880s, racing to find and describe new species before the other. The competition was bitter and often scientifically sloppy — species were named from incomplete material, descriptions were rushed, and errors accumulated.

The most complete early Stegosaurus specimen — the one that finally established the animal's anatomy clearly — was collected by Marshall P. Felch at Garden Park in 1886 and described by Marsh as Stegosaurus stenops. This specimen, now at the Smithsonian, remains the type specimen of the species that represents the genus. The 'stenops' species designation means 'narrow-faced,' referring to features of the skull.

Garden Park is now a National Natural Landmark, and DMNS runs field seasons there. The site is accessible northeast of Cañon City and open to visitors. The town has leaned into its paleontological identity — the Dinosaur Depot Museum on Main Street shows what's come out of these quarries across 150 years of collecting.

Colorado's 1982 designation of Stegosaurus was among the earliest in the country — the category of state dinosaur barely existed yet. The choice was not a difficult one: Colorado had the discovery sites, the formations, and a century of museum infrastructure already built around this animal.

By 1982, the Denver Museum of Natural History — now DMNS — was already the central institution for Morrison Formation research. Colorado's connection to Stegosaurus ran from the 1877 original collection at Morrison through the 1880s Garden Park excavations through a century of museum work. The designation reflected that record rather than creating it.