CHICAGO (CBS) — Twenty-five years is just a drop in the bucket for a 65-million-year-old fossil, but it’s still a big milestone for the Field Museum, which is celebrating what it calls “unearth day” for Sue the T-Rex.

“We love Sue. I’m a big dinosaur fan. I want to be a paleontologist,” said 9-year-old Carter Langer, as he visited the Field Museum on the 25th anniversary of Sue’s discovery.

Sue has been the top attraction at the Field Museum for 15 years, since the museum bought it at auction for $8 million.

Museum spokeswoman Emily Waldron said Sue is the largest, most extensive, and best-preserved Tyrannosaurus rex skeleton ever found. She was named for Sue Hendrickson, the paleontologist who found the fossil in a cliff face during a search in the Black Hills of South Dakota in 1990.

“It was the last day, and the jeep got a flat. The rest of the team was going to go in, and fix the flat. Sue thought she wanted to do one more pass-through of the area,” Waldron said. “She saw something in the rock that she just immediately knew was fossil.”

To celebrate Sue’s “unearth day,” the Field Museum is promoting a recently-added feature: children’s birthday parties at the museum. You can find more information on their website.