"When the S.P.R.R. (Southern Pacific Railroad) came through southern Arizona in 1880, the town of Benson was founded. The new town, at a somewhat different location for that of the earlier stage station (see Ohnersorgen Stage Station) was the rail shipping point for the booming new town of Tombstone to the south. Benson was named for Judge William B. Benson of California, a friend of Charles Crocker, president of the railroad. Judge Benson spent many years in the mining regions of the West."
P.O. Est. July 26, 1880.
Barnes, Will C.; Granger, Byrd (ed.) Arizona Place Names University of Arizona Press. 1960. p. 30
From: http://jeff.scott.tripod.com/benson.html - Thanks!