Regional Road 174 was created on April 1, 1997 when the Ministry of Transportation of Ontario transferred the responsibility of maintenance and upkeep along of Highway 17 east of "the split" with Ontario Highway 417 to Trim Road (Regional Road 57), a process commonly referred to as "downloading". Despite the protests of the city that the road served a provincial purpose, a second round of transfers saw Highway 17 east of Ottawa downloaded entirely on January 1, 1998 adding to the length of Regional Road 174. The Trans-Canada Highway designation was taken from the former Highway 17 and applied to the existing Highway 417 freeway in 1997-98. Ottawa immediately renumbered the transferred sections of Highway 17.