The highway, as SR-186, was formed in 1935, initially going from what is now US-89 in downtown east on 400 South, west on 200 South after a gap, and south on 1300 East to US-40, now 2100 South. Portions of this route were signed as US-40 Alternate. By 1954, Foothill Drive existed in its current state and US-40A, as well as the legislative and unsigned SR-186 designation, was routed along that road. At one point, the highway extended west to the Salt Lake City International Airport (well after US-40A was truncated), but this connection was lost in 2007 when SR-186 was aligned to cover all of former SR-184, which was decommissioned that same year.