The American mastodon was a distant relative of the ancestors of the elephant. During the Pleistocene it ranged from Alaska to Florida. Mastodons differ from mammoths by their smaller size and lower-crowned ridged teeth for browsing rather than grazing. Mastodons from Rancho La Brea tend to be smaller than those found at other localities. They are quite rare and are represented by at least 15 individuals.
A partial skeleton of a baby mastodon was discovered in early 2011 in Box 14 of Project 23. This left maxilla includes the 3rd and 4th premolars. The tiny tusk is missing from its socket.