In 1938, Roland T. Bird traveled across the United States searching for fossils for the American Museum of Natural History in New York, and the dinosaur tracks he found here sent shockwaves through the scientific world. Buried just beneath the Paluxy River were hundreds of massive, saucer-shaped sauropod tracks, the first ever identified, along with numerous three-toed theropod tracks. Based on this find, Bird developed the theory that sauropods walked on land. It took Bird and his crew two years to excavate the ancient tracks, using sandbags to hold back the river as he chiseled the trackways from the bedrock, broke them into pieces, carefully cataloged each one, and wrapped them in plaster-coated burlap for safe transport to New York. Hundreds of people came to see the trackway excavation at Dinosaur Valley in the summer of 1940.