I've caught a couple at 1lb and some 13 inchers. Caught about 20 in one day one time at a local creek. When they are in environments that get a lot of smaller bait fish, shiners and smaller creek chubs they can grow quite large as they are provided with a large amount of food.
BTW make sure that you are catching a Creek Chub and not a Fallfish. These two fish look almost identical at large sizes, but Fallfish can grow much larger.
To distinguish Creek Chubs from Fallfish check the dorsal fin/fin on the top of the fish' body, if it has a black dot, it is a Creek Chub, no black dot means it's another species most likely Fallfish. At my local Creek last year I spotted a Fallfish that was easily over 5lbs... just imagine a 5lb Creek Chub swimming around
This is one of my better Creek Chubs.... 13"