The Riverside Shipyard was the ground-based Starfleet shipyard 2-1A located in Riverside, Iowa, Earth. The Riverside construction zone was under the SFC Division, United Federation of Planets, Sector 47. (Star Trek)
In the mid-2250s, the USS Enterprise was constructed at the Riverside Shipyard. The shipyard was also an embarkation point from where Starfleet Academy cadets would travel to their training facilities. According to the ship's dedication plaque, although constructed in Iowa, the Enterprise was launched from the San Francisco Fleet Yards.
In 2255, James T. Kirk boarded the military shuttle Bardeen at the Riverside Shipyard after Christopher Pike dared him to enlist in Starfleet and do better than his father the night before at the nearby Shipyard Bar. (Star Trek)
According to co-writer Roberto Orci: "Shortly after the heroic death of George Kirk, the Iowa shipyards were erected by Starfleet to honor and commemorate the sacrifice. Hence, the Kelvin salt shaker in the diner, etc...." 
According to the novelization of Star Trek, the decision was more a matter of location, as central Iowa was close to the Mississippi River and a still-industrial Midwest, but sufficiently isolated that a catastrophic accident would endanger few people outside of the shipyard itself.