Thanks to PressboxOnline, here are bunch of facts and figures about the AFC North, whose history started with the realignment of the NFL from six to eight divisions in 2002. The Baltimore Ravens were put into this division along with the Pittsburgh Steelers, Cincinnati Bengals and Cleveland Browns to form what is now one of the tougher divisions in the league, but only based on two of the four teams in it. There's a pretty huge disparity between the Ravens/Steelers and the Bengals/Browns, but the thought of having to play both Baltimore and Pittsburgh twice every season makes the teams not in the AFC North,... happy not to be in the AFC North.
When the Ravens were part of the realignment, there was thoughts that they should stay in the same division as their heated rival, the Tennessee Titans as well as the Jacksonville Jaguars, with whom they had some great, close contests over the previous few seasons. Then, of course, there was the natural rivalry with the Indianapolis Colts.
However, with Pittsburgh, Cleveland and Baltimore moving from the NFC to the AFC when the two leagues (NFL & AFL) merged, it was only natural to keep them together for old-time's sake. The rest, as they say, is history.