For at least forty thousand years, asphalt has seeped up through this ground, and you can still smell it in the middle of one of the most urban neighborhoods in America. For at least forty thousand years, crude asphalt has been seeping up through the ground here from natural petroleum deposits below, forming sticky pools that trapped animals that came to drink what looked like water — saber-toothed cats, dire wolves, mammoths, giant ground sloths, and American horses, along with the birds and insects that fed on their carcasses. More than three and a half million fossils have been excavated here, representing over 650 species.
The asphalt is still seeping; you can smell it, and on hot days it softens enough that small animals still occasionally become trapped. The discovery of the fossil treasure was confirmed in 1901, and excavations have continued almost ever since. Project 23, an ongoing excavation that began when an underground parking garage was planned for the museum, has yielded twenty-three fossil deposits so far.
Look at the pool of dark asphalt near the museum entrance; the model mammoths in the tar are showing you exactly what this scene looked like ten thousand years ago.