Actually, the role if not the name was first occupied full-time with FDR's VC-54 (Douglas DC-4 IIRC) "Sacred Cow." (The part-timer previously was Dixie Clipper, one of Pan Am's Boeing 314s.) Truman had a VC-118 (DC-6), the Independence, and then Ike had several Connies named Columbine (if memory serves the one at NMUSAF is C-III).
Apologies for any glitches, it's been a long and annoying (seriously, it's the kind where I'm damn glad I'm a guy because if I had to fight with PMS on top of EES*, somebody might get hurt) day, and I'm typing half-fatigued relying on childhood memories of the USAFM Presidential hangar.
*Everybody Else's S---.