English: Assessment of genomic diversity in the African-American population by studying three genotyped cohorts comprising 3,726 African-Americans. An estimated 82.1% of ancestors to African-Americans lived in Africa prior to the advent of transatlantic travel, 16.7% in Europe, and 1.2% in the Americas, with increased African ancestry in the southern United States compared to the North and West. Inferred regional ancestry proportions for the HRS (Health and Retirement Study) and SCCS (Southern Community Cohort Study) cohorts: (A) African, (B) European, and (C) Native American ancestries. (D) Local ancestry assignment along the autosomes for an African-American individual from HRS. (E) Comparison of the African ancestry proportions in the HRS, SCCS, and 23andMe stratified by state. Error bars represent 68% confidence intervals derived using sample bootstrap and, thus, do not account for possible sampling biases. 23andMe proportions are from Bryc K (2015) and are reported for ease of comparison.