sentences:  The building was then converted to its current use as a recreation center though much of the exterior was preserved and retained the Auditorium name on the building.For countless generations, the Native American residents at the confluence of the Big Sioux River with the Missouri River held their ceremonies, performances, and sporting events primarily outdoors, without need of specialized structures.The fourth Treaty of Prairie du Chien in 1830 forced them to leave Iowa, and forty years later the new White residents built the first in a series of five major indoor venues for Sioux City