The map is based on data from 2010, and includes any individual who reported descent from two or more races on their Census form. Multiracial Americans make up a total of about 2.9% of the population, but there is wide regional variation. The county with the highest Multiracial proportion of the population is Hawaii County, at 29.2%.
There is a clear east/west divide, with western states having an overall higher percentage of Multiracial americans. On the other hand, the Deep South has low levels of people identifying with multiple races. For example, Mississippi only has a handful of counties where the Multiracial population is above 1.5%.
The big outlier is Oklahoma. The surrounding states have average levels of Multiracial people, but in Oklahoma 7% of the population is multiracial, the highest rate outside of Hawaii (24%) and Alaska (8%). There is also a clear divide in Oklahoma, with the multiracial population increasing as you go from west to east across the state. This large Multiracial population is a legacy of the frequent intermarriages between White, Native American, and Black individuals, both in the present day, and going back to the state’s historical origin as “Indian Territory.”
Minnesota Population Center. National Historical Geographic Information System: Version 2.0. Minneapolis, MN: University of Minnesota 2011. http://www.nhgis.org