The section of MN 15 between New Ulm and the Iowa state line was originally Minnesota Constitutional Route 15, dating back to 1920.
The section of MN 15 between St. Cloud and Kimball was originally part of Constitutional Route 24.
The middle section of MN 15 was authorized in 1933, the northernmost section in 1950. This northerly section was originally part of old MN 152 and was routed through downtown St. Cloud. Now, it bypasses central St. Cloud to the west side of town.
By 1940, only two short gravel sections of MN 15 remained, both paved by 1953.
In the 1970s, MN 15 through the St. Cloud area was planned to be constructed as a freeway, providing a high-speed connection between I-94 and US 10]]. However, funding fell short of completing the freeway beyond MN 23 and County Road 75 (CR 75, 2nd Street South). As a result, it was eventually decided that right-of-way needed to build interchanges would be sold off so the remaining segment of MN 15 across the Mississippi River, connecting to US 10, could be built. Therefore, from 2nd Street South to US 10, the highway is currently built as an expressway with signalized intersections.[3]
As of now, MN 15 is able to serve traffic, with stretches posted at a 65 mph (105 km/h) speed limit. However, continuing increases in traffic in the St. Cloud area will require the highway to be eventually converted to a freeway in the long term (post 2030).