Barnum Brown found five Tyrannosaurus rex skeletons in the Hell Creek area of Montana between 1902-1905. These skeletons were partial, but very valuable finds. The most complete and biggest Tyrannosaurus rex skeleton was found in the Hell Creek Formation in South Dakota by Susan Hendrickson in 1990. The skeleton was named Sue in honor of the amateur paleontologist. The Tyrannosaurus sold at auction for $7.6 million and the money was given to Maurice Williams, the orginal owner of the land. Sue is now at the Field Museum of Natural History. Several other Tyrannosaurus rex skeletons were found in the same area, an indication that these dinosaurs traveled in packs.

Another skeleton named Stan was found in the same area after 30,000 hours of digging. This Tyrannosaurus rex was 65% complete but had the interesting characteristics of a healed broken neck as well as a hole in the skull from another Tyrannosaurus rex tooth.

The Hell Creek Formation has yielded many Tyrannosaurus rex skeletons and some are being analyzed for the presence of DNA that might help solve some of the mysteries surrounding this fascinating creature.