I am going to be visiting my sister soon. She lives in Oklahoma near, Oklahoma City. Does anybody know of any rivers I could wade for smallmouth near that area?

There's no place that I know of nearby, but the Glover River 4hrs drive to the southeast close to the Ouachita Mountains is an excellent smallmouth fishery.  It's beautiful scenery over there as well.  The Blue River is closer to the south near Tishomingo, and supposed to have smallies, but I don't know much about the fishing there.