The Random House publishing company entered the reference book market after World War II.

[3] For medical and psychological in the dictionary, many physicians in the New York City area where Random House was headquartered gave their assistance.

[3] In the late 1950s, it was decided to publish an expansion of the American College Dictionary, which had been modestly updated with each reprinting since its publication.

Under editors Jess Stein and Laurence Urdang, they augmented the American College Dictionary with large numbers of entries in all fields, primarily proper names, and published it in 1966 as The Random House Dictionary of the English Language: The Unabridged Edition.

When the American College Dictionary was first published, The Journal of the American Medical Association called it "more modern than any other similar book" and that the dictionary had included "considerable information not available in other dictionaries, such as rules for punctuation, proofreader's marks and notes on footnotes and bibliography".