This from NAVSOURCE ONLINE:
The keel of the fifth ship of the Iowa class, the Illinois (BB-65), was laid down on 15 January 1945 at Philadelphia Navy Yard. By 7 July the construction had progressed this far and the ship was officially cancelled a month later, on 11 August 1945, only about 22 % complete. Nothing was done with the ship after that and the remains were finally scrapped, this starting in September, 1958.
The Illinois and her sister Kentucky BB-66 differed from the four completed ships in that their design called for an all welded construction. This would have saved weight and increased strength over a combination riveted/welded hull like was employed on the completed ships. There was thought of redesigning the hull with a "Montana class " type protection system for added torpedo protection. This was rejected and the two ships were being built along the regular Iowa class hull design.