[5] Should a highway run through a municipality, IDOT is authorized to choose a route through the municipality in order to make a route contiguous for through traffic.

These initial 46 route numbers marked the major infrastructure roads desired by the state legislature in 1918.

Remarkably, many of these numbers still exist on the original or nearby alignment.

In 1924, additional State Bond Issues were authorized for SBI Routes 47 through 185.

These route numbers were originally assigned and grouped to specific regions of the state.