Reducing racial/ethnic disparities is a primary objective of the National Alzheimer’s Plan (NAPA), yet direct comparisons within large samples representing diversity of the United States are lacking. Dementia incidence from January 1, 2000 to December 31, 2013 and a 25-year cumulative risk in 274,283 health care members aged 64+ (n = 18,778 African-American, n = 4543 American Indian/Alaska Native [AIAN], n = 21,000 Latino, n = 440 Pacific Islander, n = 206,490 white, n = 23,032 Asian-Americans). Cox proportional hazard models were adjusted for age, sex, medical utilization, and comorbidities. Dementia incidence (n = 59,555) was highest for African-Americans (26.6/1000 person-years) and AIANs (22.2/1000 person-years); intermediate for Latinos (19.6/1000 person-years), Pacific Islanders (19.6/1000 person-years), and whites (19.3/1000 person-years) and lowest among Asian-Americans (15.2/1000 person-years). Risk was 65% greater for African-Americans (hazard ratio = 1.65; 95% confidence interval = 1.58-1.72) versus Asian-Americans. Cumulative 25-year risk at age 65 was as follows: 38% African-Americans, 35% AIANs, 32% Latino, 25% Pacific Islanders, 30% white, and 28% Asian-Americans. Dementia rates varied over 60% between groups, providing a comprehensive benchmark for the NAPA goal of reducing disparities.