Bill O’Reilly. He’s my character is Fallout 3, which is my biggest (only, really) exposure to anything remotely 1950s. He’s an old, gay black man.
If I thought about the for real 50s for a minute, Elvis.
Joseph McCarthy.
The man who made the 1950s so unpleasant for so many.
Elvis … then after a short delay … McCarthy.
McCarthy.
Going against the grain here with Frank Sinatra. Maybe Boomers see the 1950s as the beginning of an era, but I tend to see it as the end of an era. Elvis spearheaded the new era, while Sinatra led the rearguards of the old one.
First one to mind was Elvis Presley, because “the 1950s” to me is a cultural reference more than historical. If you said, “major event of the 1950s” I’d have first thought of Sputnik, the Korean War (partly because of MAS*H) and the development of the H-Bomb.
Elvis.
However, Marilyn Monroe and James Dean would be close behind.
Diefenbaker
I had to think about it for a second, just to come up with names from the 50’s but Elvis was the first one I thought of. I’m way to young (33) for Eisenhower to come to mind. If I was pressed for more names, they’d be musical acts, maybe some actors (Lucille Ball/Marilyn Monroe right off the top of my head). But Elvis is the first.
Elvis, Eisenhower.
This is a really eye-opening thread. I was born in the early 70s, and most of the names here are 1960s to me (due to my own ignorance of both decades).
I wouldn’t have been able to come up with an answer to the OP.
Good Dog. 
“Biff”.
Another Eisenhower here.
Marilyn Monroe, then Elvis.
Beaver Cleaver.
Another vote for this.
Buddy Holly, then McCarthy.
Shirley. Probably because of Laverne & Shirley. I can’t stand Elvis.