Between Rock River and Medicine Bow, US-30 runs beside a long, low ridge of tilted rock. It looks like very little. In 1877 it became the richest dinosaur ground yet found anywhere, and the start of Wyoming's first bone rush.
The ridge and the letter
Como Bluff is an anticline, a ridge of rock layers bowed upward and worn open along its crest, so that miles of the Morrison Formation lie exposed along its flanks. The Morrison's pale green, purple and gray mudstones were laid down by rivers on broad floodplains about 150 million years ago, in the Late Jurassic, and the animals that died there were buried whole or in pieces. The first transcontinental railroad ran along the foot of the bluff, with a station at Como.
In 1877 two Union Pacific men at the station, William Reed, a section foreman who had hunted meat for the construction crews, and William Carlin, the station agent, found big bones weathering out of the hill. That July they wrote to Othniel Charles Marsh, the paleontologist at Yale, signing with false names and mailing the letter from Laramie to keep their find quiet. Marsh, whose rival Edward Drinker Cope of Philadelphia already had collectors in the West, sent an assistant out to see and hired them both.
Marsh against Cope
For the next dozen years Como Bluff was a front line of the feud known as the Bone Wars. Marsh's crews worked the bluff from 1877 to 1889, opening one quarry after another, and Reed became his most productive collector. Carlin went over to Cope, whose men were digging on the same ridge by 1879. The camps spied on each other and poached each other's diggers, and in 1879 Marsh told Reed to destroy a worked quarry rather than leave anything in it for Cope.
What came out of the ground filled the great museums. The bluff's quarries yielded Stegosaurus, Allosaurus and several kinds of long-necked sauropod, and in 1879 Reed found the partial skeleton Marsh named Brontosaurus excelsus, the thunder lizard. Paleontologists later folded Brontosaurus into Apatosaurus; a 2015 study argued it deserved its own name again, and many now agree. The bluff also gave up some of the best-known Jurassic mammals, small animals that lived underfoot. Como Bluff bones stand in the Yale Peabody Museum, the Smithsonian, the American Museum of Natural History and the Carnegie Museum. Reed went on to collect for the University of Wyoming, and the Allosaurus he dug still stands in its geology museum in Laramie.
What is there now
Most of the bluff is private ranchland, and the old quarries have long since been backfilled or weathered in. It is a National Natural Landmark and listed on the National Register. For ninety-four years the roadside stop was the Fossil Cabin, which a homesteader named Thomas Boylan built beside the Lincoln Highway in 1932 out of 5,796 dinosaur bones he had gathered from the area. He ran it with a gas station, and Ripley's Believe It or Not called it the world's oldest cabin. Vandals had been chipping bones out of its walls, and in May 2026 the whole fifty-ton building was moved seven miles west to the Medicine Bow Museum. The bones, at least, are still about 150 million years old.