These two publications are excellent general-purpose collections of data on the U.S., with some international coverage.
Statistical Abstract of the United States. U.S. Census Bureau.
Annual publication is THE single most useful statistical collection.
Historical Statistics of the United States. Cambridge University Press.
The following are specialized collections of data on racial and ethnic populations in U.S.
Race/Ethnicity (Population Estimates). U.S. Census Bureau.
Race Data. U.S. Census Bureau.
Racial and Ethnic Diversity; Asians, Blacks, Hispanics, Native Americans, and Whites.
There are additional collections of statistical information on the library's Statistical Sources page.