We find that many self-reported European Americans, predominantly those living west of the Mississippi River, carry Native American ancestry (Figure 3B). We estimate that European Americans who carry at least 2% Native American ancestry are found most frequently in Louisiana, North Dakota, and other states in the West. Using a less stringent threshold of 1%, our estimates suggest that as many as 8% of individuals from Louisiana and upward of 3% of individuals from some states in the West and Southwest carry Native American ancestry (Figure S7).