Of course, I am just going by what I have read from that period, I defer to anyone who actually lived during that time. In 1955, what was the more commonly used term, white or Caucasian?
It depended on the setting and the context. I was born in 1953 and grew up in the North, in the city of Chicago. I think that in common parlance whites would refer to themselves as "white," simply because that was easier to say than the more scientifically-based "Caucasian." And in common parlance they would refer to blacks as "black," for the same reason--unless they wanted to say something derogatory, in which case they would use "n*gger."
In more formal language--newspapers, e.g., which in those days were more formal than today's USAToday-speak--the term "Negro" would be used, and there was nothing racist about it. It was a neutral term. I'm sure this is Andy Rooney's frame of reference.
In the mid-to-late '60s "Negro" gave way to "black," with the advent of the "Black Power" and "Black is beautiful" movements. Then "Afro-American" came along in the early '70s," and in the last 20 years or so that has morphed into the sesquipedalian "African-American."