The species now known as Edmontosaurus annectens was named in 1892 as Claosaurus annectens by Othniel Charles Marsh.
This species is based on USNM 2414, a partial skull-roof and skeleton, with a second skull and skeleton, YPM 2182, designated the paratype.
Both were collected in 1891 by John Bell Hatcher from the late Maastrichtian-age Upper Cretaceous Lance Formation of Niobrara County (then part of Converse County), Wyoming.
This species has some historical footnotes attached: it is among the first dinosaurs to receive a skeletal restoration, and is the first hadrosaurid so restored; and YPM 2182 and UNSM 2414 are, respectively, the first and second essentially complete mounted dinosaur skeletons in the United States.
YPM 2182 was put on display in 1901, and USNM 2414 in 1904.

In the first decade of the twentieth century, two additional important specimens of C. annectens were recovered.
The first, the "Trachodon mummy" (AMNH 5060), was discovered in 1908 by Charles Hazelius Sternberg and his sons in Lance Formation rocks near Lusk, Wyoming.
Sternberg was working for the British Museum of Natural History, but Henry Fairfield Osborn of the American Museum of Natural History was able to purchase the specimen for $2,000.
The Sternbergs recovered a second similar specimen from the same area in 1910, not as well-preserved but also found with skin impressions.
They sold this specimen (SM 4036) to the Senckenberg Museum in Germany.
The species now known as Edmontosaurus annectens was named in 1892 as Claosaurus annectens by Othniel Charles Marsh. This species is based on USNM 2414, a partial skull-roof and skeleton, with a second skull and skeleton, YPM 2182, designated the paratype. Both were collected in 1891 by John Bell Hatcher from the late Maastrichtian-age Upper Cretaceous Lance Formation of Niobrara County (then part of Converse County), Wyoming. This species has some historical footnotes attached: it is among the first dinosaurs to receive a skeletal restoration, and is the first hadrosaurid so restored; and YPM 2182 and UNSM 2414 are, respectively, the first and second essentially complete mounted dinosaur skeletons in the United States. YPM 2182 was put on display in 1901, and USNM 2414 in 1904.
In the first decade of the twentieth century, two additional important specimens of C. annectens were recovered. The first, the "Trachodon mummy" (AMNH 5060), was discovered in 1908 by Charles Hazelius Sternberg and his sons in Lance Formation rocks near Lusk, Wyoming. Sternberg was working for the British Museum of Natural History, but Henry Fairfield Osborn of the American Museum of Natural History was able to purchase the specimen for $2,000. The Sternbergs recovered a second similar specimen from the same area in 1910, not as well-preserved but also found with skin impressions. They sold this specimen (SM 4036) to the Senckenberg Museum in Germany.
Edmontosaurus annectens