When the US Highway system was being put together in 1925 and 1926, the powers that be decided that the “major” routes would be those that end in 0 or 1. Indiana, in its place as “Crossroads of America,” would be home to quite a few of these. Given the width of the United States, the fact that two of the major north-south routes would run through the state might have been a bit strange. However, that is what happened.
When the second batch of new state roads were being commissioned starting in 1919, the route connecting Evansville, Vincennes, Terre Haute, Rockville, Attica, and Hammond on its way to Chicago was given the original state road 10 designation. This made SR 10 the longest such road in the state. With the Great Renumbering, it acquired its current designation, although the road would be moved in many places.