I have no direct information that the Opera House was the location of the Twain-Cable reading of January 13, 1885, but I found this listing in the Hannibal City Directory 1885-86.  Hannibal Opera House Co., cor of 5th and Center, J.B. Price, manager, office at F. & M. bank.

 Image:  Hannibal, Missouri: Bluff City Memories  By Steve Chou

 "The Park Opera House stood at the corner of Fifth and Center. Purchased by the  Hannibal Masonic Lodge in 1915, it was used as the Masonic Temple for nearly 75  years. It was razed for a parking lot in 1992. In its day, such notables as Lillian Russell, Buffalo Bill, and Harry Houdini performed here. This stereopticon photo by Calvin Jackson shows the opera house nearing completion in 1882."  (page 16).