The current size champion was found in the summer of 1997 in a Late Cretaceous period bone bed near the Fort Peck reservoir in Montana. This area is in the Badlands of eastern Montana. The remains were found in the Hell Creek rock layer, a geological formation well known for its dinosaur bones. The site appears to have been a former river channel. The bones of dead dinosaurs were washed into the channel and collected in one place. This skeleton, though only partially excavated, appears to be nearly complete and is the largest specimen of a Tyrannosaurus rex yet found. Its pubis bone is at least 52 inches (133 centimeters) long. The previous largest known Tyrannosaurus rex skeleton had a pubis bone approximately 48 inches (122 centimeters) long. The skull of this animal measures approximately 6.6 feet (2 meters) long.

There was another astounding discovery in 2001: a half-complete skeleton of a juvenile Tyrannosaurus was discovered in the Hell Creek formation in Montana, by a crew from the Burpee Museum of Natural History of Rockford, Illinois. It was named “Jane the Rockford T-Rex” and was initially considered the first known skeleton of the pygmy tyrannosaurid Nanotyrannus. After several leading experts examined the fossils, however, the consensus is that it is probably a juvenile Tyrannosaurus rex, the most complete and best-preserved to date.

There are also U.S. dinosaur fossils that still have to be confirmed and/or analyzed. For example, in 2001, Jack Horner revealed that he had discovered a Tyrannosaurus rex around 10 percent larger than the dinosaur “Sue” that is at the Field Museum in Chicago. Horner calls the specimen C. rex (or “Celeste,” after his wife), but there is still work to do on the fossil.

Although discovered in the 1960s, researchers at Montana State University in 2006 claimed to have found the largest Tyrannosaurus skull yet. It measures 59 inches (150 centimeters) long compared to the 55.4 inches (141 centimeters) of “Sue’s” skull, making it the largest discovered so far.