I found an excellent history of Football Rules, including these dates and rules changes:
- No tackling out-of-bounds.
- No Hurdling or piling on after play called dead.
- No tackling below the knee.
- No stricking the ball carrier in the face.
- No locking of legs, except for the two players on either side of the center.
- Referee called the end of the play.
- Offense had to have 6 players on line of scrimage.
- Only one player in motion before the snap.
- Any player moving from the line of scrimage had to be replaced prior to the snap of the ball.
- The length of the game shortened to 2 thirty minute halves.
- The number of yards need for a first down increased from 5 to 10.
- Neutral zone increase to length of the ball.
- Legalization of the forward pass.
- If the pass was incomplete, it was a turnover.
- A pass completed in the endzone was a touchback for the defending team (turnover)
- If the ball wasn’t thrown within 5 yards, either side of the middle of the field, or hit an ineligble receiver, it was a turnover. Hash marks were added.
- Seven players on the line of scrimage. End of mass-formation plays.
- No pushing or pulling the ball carrier.
- No interlocked interference.
- No crawling.
- Flying tackle banned.
- Score for forfeited game set at 1 point.
- A player leaving the game could not return until the start of the next quarter.
- Forward passes limited to 20 yards in length or under.
- Team had 4 downs to make a firstdown. (10 yards)
- Length of field reduced to 100 yards from 110 yards. 10 yard endzone created behind each goal.
- Value of a touchdown increased from 5 to 6 points.
- All distance restrictions for a forward pass were removed.
- A pass completed in the endzone was now a touchdown and no longer a turnover.
- An incompleted pass was a loss of down and no longer a turnover.