Mahaska County Courthouse was completed in 1886 at a cost of $132,158 and was dedicated by John F. Lacey, an Oskaloosa congressman and founder of the National Parks System. In 1916, the courthouse was painted gray at a cost of $1,009, but years later the paint was removed to reveal the red brick and white foundation seen today. In 1918, a 1,200-pound weight from the tower clock broke loose, crashed through the third-floor ceiling, and shattered two stone steps, which were replaced with the wooden ones there today. In 1934, the original ornamental gabled entryway was removed, and its two large columns were moved to a private residence in Oskaloosa at 1215 C Avenue West. The courthouse was also the site of the famous "shotgun trap" trial in Katko v. Briney, which reached the Iowa Supreme Court in 1971, drew national media attention, and became a staple of law school classes across the country.