21. Transportation maps. Iowa, transportation map, railroads, highways, canals, air lanes, dredged channels, and pipe lines; highways corrected to Feb. 1, 1934. Scale 1:250,000, approximately 1 in.=4 m. Bookmark Corporate/Agency Authors: Public Roads Bureau and Agriculture Department Publisher: Public Roads Bureau Date: 1934 SuDoc number: A 22.9/2:Io 9/sh.1-8