Carver had nothing to do with peanut butter. The Incas invented the stuff and , in the 19th century, it was introduced by a physician (unbeknownst to CArver) at the Chicago Exposition.
Julia Chandler supposedly introduced the concept of the PBJ sandwich in a cookbook in the early 1900's and then, thanks to the cheapening cost of making the stuff based on an industrial peanut smasher introduced by the Gamble Brothers (Procter and Gamble fame) and Gustav Papendick, who invented sliced bread, the PBJ achieved major diet status in the early 1920's.
The original PB sammich was with watercress. Try that sometime. If you have a clean creek nerby, go pick some watercress and make a toast sammich with PB and cress. (maybe even a real thin slice of onion R-E-A-L thin so onion doesnt take over the flavor(or else use a Walla Walla or some other dessert onion)