Adler was born in Van Buren, Arkansas, a graduate of University of Pennsylvania in 1883 and gained a Ph.D. from Johns Hopkins University in 1887, where he taught Semitic languages from 1884 to 1893. He was employed by the Smithsonian Institution for a number of years, with a focus on archaeology and Semitics, serving as the Librarian from 1892-1905. He was a founder of the Jewish Welfare Board, and an editor of the Jewish Encyclopedia, and part of the committee that translated the Jewish Publication Society version of the Hebrew Bible published in 1917. At the end of World War I, he participated in the Paris Peace Conference in 1919. His many scholarly writings include articles on comparative religion, Assyriology, and Semitic philology.