On August 12, 1990, fossil hunter Susan Hendrickson discovers three huge bones jutting out of a cliff near Faith, South Dakota. They turn out to be part of the largest-ever Tyrannosaurus rex skeleton ever discovered, a 65-million-year-old specimen dubbed Sue, after its discoverer.

Amazingly, Sue’s skeleton was over 90 percent complete, and the bones were extremely well-preserved. Hendrickson’s employer, the Black Hills Institute of Geological Research, paid $5,000 to the land owner, Maurice Williams, for the right to excavate the dinosaur skeleton, which was cleaned and transported to the company headquarters in Hill City. The institute’s president, Peter Larson, announced plans to build a non-profit museum to display Sue along with other fossils of the Cretaceous period.

In 1992, a long legal battle began over Sue. The U.S. Attorney’s Office claimed Sue’s bones had been seized from federal land and were therefore government property. It was eventually found that Williams, a part-Native American and member of the Cheyenne River Sioux tribe, had traded his land to the tribe two decades earlier to avoid paying property taxes, and thus his sale of excavation rights to Black Hills had been invalid. In October 1997, Chicago’s Field Museum purchased Sue at public auction at Sotheby’s in New York City for $8.36 million, financed in part by the McDonald’s and Disney corporations.

Sue’s skeleton went on display at the Field Museum in May 2000. The tremendous T.rex skeleton—13 feet high at the hips and 42 feet long from head to toe, with a 2,000-pound skull and 58 teeth—is displayed in a special exhibition space.

Sue’s extraordinarily well-preserved bones have allowed scientists to determine many things about the life of T.rex. They have determined that the carnivorous dinosaur had an incredible sense of smell, as the olfactory bulbs were each bigger than the cerebrum, the thinking part of the brain. In addition, Sue was the first T.rex skeleton to be discovered with a wishbone, a crucial discovery that provided support for scientists’ theory that birds are a type of living dinosaur.