I remember my grandparents visiting Vegas in the mid 1970’s and staying at the orleans Why does Wikipedia say it opened in 1996 ? Was it rebuilt ?

Yes it open in 96 , no rebuild yet

The Orleans was a new hotel in 1996 built on long vacant land.....it was never rebuilt.

You may be mistaken. I doubt this building was here in the 70s. Perhaps another location w similar name. 1996 is correct for this specific hotel casino