<https://www.americanroadmagazine.com/forum/topic/1933-building-the-illinois-national-road/#comment-17954>
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"Jim, \n  \nThis is not solid, but I think you can point to post WW1 for that road construction. During 1917-1919 it was tough to get road building materials and equipment because they were going to the war effort. I think the same applies to road workers. The 1920 season was the first after the war to be a big construction season. \n  \nThe Caterpillar tractor is pretty big, and appears gas powered, pointing to WW1 or after. The Caterpillar name was initiated by the Holt Manufacturing Company and there is a 1920 Holt manual with the Caterpillar logo on Google Books. Unfortunately it does not include a photo of the 120hp machine itself, but Holt had plants in Stockton, California and Peoria, Illinois. \n  \nThe one thing that is a bit of a fly in the ointment is that we don't know what paving material Illinois was favoring in 1920, but we know from publications of the time that 1920 Illinois state road construction bids included brick and concrete, so brick was a definite possibility, even if concrete may have been favored. \n  \nI have more than exhausted my knowledge, and I am left admiring your find.  Thanks for sharing!! \n  \nDave \n  \nKeep the Show on the Road \n"
<https://www.americanroadmagazine.com/forum/topic/1933-building-the-illinois-national-road/?tab=comments#comment-17947>