well, when professional football became profitable in the 1960's there was still only the nfl. then someone came up with a plan to form a rival league called the afl (american football league). they finally decided to merge in 1970. nfc teams were the original nfl, and afc teams were originally afl. so combined they are the nfl. i think the browns, colts and steelers switched to become afc teams to make the numbers even (they both have 13 teams), but i am not sure how they decided those would be the three to switch.
at 8:19 PM on Jan. 30, 2011