In 1919 when the state highway system was first numbered , the main north -- south highway through Pontiac was numbered M - 10 .
North was renumbered to US 10 seven years later when the United States Numbered Highway System was created .
In 1919 when the state highway system was first numbered , the main north -- south highway through Pontiac was numbered M - 10 , and it was renumbered to US 10 seven years later when the United States Numbered Highway System was created .