The fall of 1988 saw the incorporation of a new nonprofit group - Clinton Area Showboat Theatre. They went to the city council and requested to lease the Showboat and to run the theatre. The summer of 1989 found CAST running the theatre. At this time the area used as a museum was converted to a shop to build sets for the theatre. Also the City of Clinton received a grant from the State of Iowa to remove the boilers and convert the front portion of the main deck to a large open room for a waiting area. In 1989 and 1990 this area was used as a rehearsal space for the Showboat Players.
The inside of the theatre finally saw some changes for the approaching summer. With help from local businesses and volunteers, the theatre received new carpeting, new wooden flooring, and new theatre seats. The seats were purchased from the DeWitt Opera House with Floors-to-go helping with the installation of basically everything.