Iowa State University Veterinarian Records, RS 22/6/0/9, University Archives, Special Collections Department, Iowa State University, http://www.add.lib.iastate.edu/spcl/arch/rgrp/22-6-0-9.html
From the heart of the Cornbelt comes the appearance of an improving horse industry. At one time considered the most important property owned by man, the horse has gone through a stage of decreased popularity and is once again making a bid for proper recognition. According to the 1944 census, Iowa has the greatest number of horses of anyone state, that is, 612,000 head. Texas follows up closely in second place with 588,000. Minnesota, third with 539,000; Missouri, fourth with 519,000, and Wisconsin with 451,000 horses stands fifth in rank.
Rooks, Cecil F.
"Light Horses In Iowa,"
Iowa State University Veterinarian: Vol. 7
, Article 3.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol7/iss3/3