I wanted to add that often east-west divisions are not based strictly on geography. Baseball fans will remember that when there were only two divisions in the National League, Atlanta and Cincinnati were in the West, although Chicago and St. Louis were in the East. I am so ancient and decrepit that I remember the 1958 Baltimore Colts/New York Giants sudden-death playoff that did so much to put the NFL on the map. Baltimore was, believe it or not, part of the Western division, although there were teams west of it (for instance, Cleveland and Detroit) in the Eastern division. It was difficult to explain to my mother why Baltimore was in the West, but presumably it was for competitive balance. But I must say that it was a little hard for me to learn later where Baltimore was.
BTW, my recollection -- I'm probably wrong -- is that as of 1958, the NFL East consisted of the New York Giants, the Philadelphia Eagles, the Washington Redskins, the Cleveland Browns, the Detroit Lions, and the Chicago Cardinals (soon to move to St. Louis). The West was the Baltimore Colts, the Pittsburgh Steelers, the Chicago Bears, the Green Bay Packers, the San Francisco 49ers, and the Los Angeles Rams. Shortly after that, the Minnesota Vikings and the Dallas Cowboys entered as expansion teams.
The AFL was also geographically odd, altough not as much. When the league began in 1960, the East had the Boston Patriots, the New York Titans, the Buffalo Bills and the Houston Oilers. The West had the Los Angeles Chargers (yes, the Chargers started there, and now they're back!), the Dallas Texans (who the Cowboys ran out of town and became the Kansas City Chiefs), the Oakland Raiders, and the Denver Broncos. Believe it or not, I'm old enough to remember all this. In my view, the AFL succeeded because there was lots of scoring in its games, and people like scoring.
I'm sure I'm misquoting, but Barron Hilton (son of Conrad Hilton, founder of the hotel chain) was once introduced as "the man who made a million dollars bringing baseball to San Diego!" He rose and said, "Thank you! But it wasn't baseball, it was football; it wasn't San Diego, it was Los Angeles; it wasn't a million dollars, but ten million dollars. And I didn't make it -- I lost it!" Still, Hilton later said that his six years owning the Chargers were the best six years of his life. Paris Hilton, btw, is his granddaughter.