When it became apparent that our regular supply of manila fiber (abaca) would no longer be available for making rope and other cordage, the Government turned to American grown hemp ( Cannabis saliva). Iowa farmers, along with those of some other states, were asked to produce fiber, an essential war material.
Wilsie, C. P. and Black, C. A.
"We're Learning About Hemp!,"
Farm Science Reporter: Vol. 5
, Article 6.
Available at: http://lib.dr.iastate.edu/farmsciencereporter/vol5/iss1/6