It was replaced in function by US 20, which that year relocated onto a freeway less than one-half mile (800 m) south of San Marnan Drive.

It intersected 4th Street, which prior to the opening of Sergeant Road in 1968 was the western end of the highway.

Continuing east, the highway widened to add a left-turn lane, which gave way to a grassy median between intersections.

Shortly thereafter, the roadway turned sharply to the northeast and passed Crossroads Mall.

Among them, Iowa 412 became East or West San Marnan Drive for its entire length; previously, it was known by Highway 412 or Frontage Road.

Early plans called for the freeway to replace Iowa 412, control of which would then revert to the City of Waterloo.