Union Depot, also known as the Grinnell Union Depot, is an historic building located in Grinnell, Iowa, United States. The Chicago, Rock Island & Pacific Railroad built the first tracks through the area in 1863, and they built a simple frame depot the same year. The Central Railroad of Iowa extended its north–south line to Grinnell nine years later, and their tracks crossed the Rock Island tracks at this location. The Minneapolis and St. Louis Railway eventually acquired the Central Railroad. The old depot became too small and this one replaced it in 1893. It was designed by the Rock Island Lines and built by a local contractor. The one-story, brick structure follows a square plan with a round corner tower at the junction of the two tracks. The tower provided the station agent with a clear view in all directions.