source: The Republican (Danville, Indiana) - issue of Thursday, July 27, 1961 - page 1, column 1:
According to a July 1961 newspaper article, Hendricks County roads were being transferred over to the new "Purdue system of numbering", whereby instead of named roads, the roads would have numbers, which corresponded to their distance from a fixed point - in this case, the Hendricks County Courthouse, which was the center of Danville. As an example, they gave the first cross-street on US 36 east of Danville - it was known as "Coon Path" or "Randolph Road", depending on who you asked, but under the Purdue system, it would be known on all maps as "County Road 110 East" - because it was 1.10 miles east of the courthouse.
The changeover required the installation of 600 new signs at all the intersections, which cost $32,500. The cost of the road signs was being paid for by area businesses, which were being allowed to place their ads on the road signs.