Some of my favorite factoids from NFL History:
1869
Rutgers and Princeton played a college soccer football game, the first ever, November 6. The game used modified London Football Association rules. During the next seven years, rugby gained favor with the major eastern schools over soccer, and modern football began to develop from rugby.1876
At the Massasoit convention, the first rules for American football were written. Walter Camp, who would become known as the father of American football, first became involved with the game.1898
A touchdown was changed from four points to five.1904
A field goal was changed from five points to four.1906
The forward pass was legalized.1909
A field goal dropped from four points to three.1912
A touchdown was increased from five points to six.
Interestingly, the NFL History site doesn’t mention what prompted the forward pass — it was an attempt to open up the game and reduce the number of injuries in the game, which still involved rugby-like scrums charging down field. Teddy Roosevelt himself demanded the changes. (They also changed the first-down distance to 10 yards, from five — in three downs.)