Elkins first taught at the University of Chicago but spent most of his career as a professor of history at Smith College in Northampton, MA, where he raised his family and eventually retired.

He attended Boston English High School and enlisted in the U.S. Army in 1943, serving in the 362nd Infantry Regiment, fighting in France but primarily Italy during World War II.

In it, Elkins made two major, and controversial, statements, the first being American abolitionists reduced their effectiveness by insisting on ideological consistency and purity, and refusing to compromise with the slave system.

The removal of personal rights and utter dependence on their owners resulted in what Elkins called "chattel slavery", which he contrasted with the system prevailing in Spanish America.

In addition, critics point out Elkins provided no data or methodology for his comparison between WWII concentration camp victims, largely white Europeans, and black Americans.

[9] The Age of Federalism: The Early Republic, 1788-1800, co-authored by Elkins and Eric McKitrick, was described as a "dazzling book," featuring an "elegant and penetrating pen portrait of Hamilton.