The Most Vaulable Player Award has been given each year since 1931 to the best player from each league, as voted by selected members of the Baseball Writers Association of America (BBWAA). Predecessors using similar voting structures existed intermittently before 1931.
In 1910 the Chalmers auto company had promised one of their cars to the major leaguer with the highest batting average that season. After a scandal in which Napoleon Lajoie was allowed to go 8-for-8 on the last day of the season to overtake ther unpopular Ty Cobb in the batting race, the Chalmers people awarded both players cars. To avoid such problems in the future, they decided not to base subsequent awards on raw statistics (which at the time, were of dubious accuracy anyway). Instead, they set up a panel of respected sportswriters, one from each major league city. Using a weighted ballot on which first place was worth seven points, and so on through eight places, one writer per team in each league voted on that league’s best player. Upon winning the car, a player was no longer eligible in later years.
The Chalmers Award lasted only four years (1911-14) but when the American League revived the idea in 1922, they used the same voting system, and many of the same writers. This was the first award to use the title “Most Valuable Player”; rather than awarding a car, they planned to build a monument on which winners’ names would be carved. The National League joined in two years later, awarding a trophy and a $1,000 bond, with these changes: There would be ten places on the ballot, and there could be repeat winners. Rogers Hornsby would be the first to repeat, winning in 1925 and 1929. The AL discontinued their award after 1928, and the NL dropped the idea after 1929.
In 1931 the BBWAA took over, using the voting structure the NL had used. In 1938 they switched to three voters per team and a more heavily weighted ballot on which first place counted for 14 points. This basic structure has lasted to the present day.