[1] He was born on December 8, 1893, in Bunkerville, Nevada, to John George Hafen, a polygamist, and Mary Ann Stucki.

Hafen edited the collection entitled The Mountain Men and the Fur Trade of the Far West which had 292 biographies by at least 20 different authors.

[9] Among the authors whose work appeared in these volumes edited by Hafen were David J. Weber, Abraham P. Nasatir and Carl P. Russell.

[11] Hafen's book Broken Hand: The Life of Thomas Fitzpatrick involved him in a complex set of interactions to bring it to publication.

In the summer of 1930 Hafen taught at the University of Colorado and also joined with John Van Male in the formation of The Old West Publishing Company, with the two of them as partners in the business.

[12] Hafen also wrote with Carl C. Rister Western America (1941) which was a text-book on the history of the Trans-Mississippi west in the United States and through 1960 was the only textbook with this as its primary focus.

[13] Among articles of note by Hafen were "The Old Spanish Trail, Santa Fe to Los Angeles" in Huntington Library Quaarterly Vol.

[3][14] Hafen's book The Overland Mail, 1849-1869 was republished in 2004 by the University of Oklahoma Press with a foreword by David Dary.