Officials from the Burke Museum confirm that construction workers uncovered a mammoth tusk that appears to date back to the Ice Age.
Joe Wells with Transit Plumbing was one of the first workers to spot the object.
"We were like, 'So, what do we do here?' You don't want to damage it or just continue on and tear it out of the ground," he said.
It's unclear how the property owner will move forward with the unique find.
"Because the fossil is on private property and does not seem to be associated with an archaeological site, it is up to the landowner to decide what they would like to do with the tusk," Dr. Christian Sidor of the Burke Museum said in a Tuesday news release.
Sidor said the discovery offers a "rare opportunity to directly study Seattle's ancient natural history." The museum has offered to excavate the tusk and provide access to scientists looking to study it.
As word of the discovery spread on Tuesday, locals wandered over to the site to get a better look at the tusk.
Tim Heithaus, whose son attends a nearby daycare, said the children were excited to get a first-hand look at Seattle history.
"It's pretty awesome," Heithaus said. "It means there was a woolly mammoth here 5,000 or 10,000 years ago. There's some cool history here in South Lake Union."
According to the museum, mammoths are ancient elephant relatives that once inhabited the ice-free lands of North America. The animals became extinct as the glaciers receded at the end of the Ice Ages, between 10,000 and 11,000 years ago.