Forty-three famous Americans

Okay, this one's probably too tough for the grownups. Got any kids or grandkids around? Let's sit back and see if they can figure out what this is.

What's the meaning of these letters?

GW JA TJ JM JM JA AJ MV WH JT
JP ZT MF FP JB AL AJ UG RH JG
CA GC BH GC WM TR WT WW WH CC
HH FR HT DE JK LJ RN GF JC RR
GB BC GB BO

Hint: See picture. Your initial hunch might be right.
Technical stuff: This is kind of a code, not a cipher.