[4] In 1856, Joseph Leidy received fragmentary remains from the Judith River Formation, collected by Ferdinand Vandeveer Hayden.

From these bones, he provided the first names for North American dinosaurs: Deinodon, Palaeoscincus, Trachodon, and Troodon (then spelled Troödon).

The generic name is derived from Greek τραχυς, trakhys, "rough", and όδον, odon, "tooth", referring to the granulate inner surface of one of the teeth.

[6] In the Bone Wars that followed, and their wake, the taxonomy of Trachodon and its relatives became increasingly confusing,[2] with one author going so far as to sink all known hadrosaur species into Trachodon except for Claosaurus agilis,[7] but as new material was described from the Rocky Mountain region, Alberta, and Saskatchewan, later authors began progressively restricting the reach of this genus.

[10][11][12] In 1936, paleontologist Charles Sternberg compared the holotype teeth of Trachodon mirabilis to those of more completely known hadrosaurids and noted that they were most similar to those of lambeosaurines.