One of Jordan's great uncles, Edward Needles Hallowell, was a commanding officer of the celebrated Civil War 54th Massachusetts of the United States Colored Troops (USCT).
After completing graduate school, Jordan spent two years as a fellow at the College of William and Mary's Institute of Early American History and Culture.
He was Professor of History at University of California, Berkeley, from 1963–82, and the school's Associate Dean for Minority Group Affairs Graduate Division, 1968-70.
As early as 1962, when he published an article on the status of 'mulattoes' in the Thirteen Colonies, Jordan's work helped to illuminate the so-called one-drop rule, a uniquely American example of hypodescent.
[4] His synthesis, White Over Black, looked at the history of race relations in the United States, and was influential for its assessment of issues of interracial sexuality.