Prior to the invention of the tractor, farmers would boast about the strength of their horse teams. In some cases, they compared horse teams pulling large loads over distance, such as a fully loaded hay cart or wagon. In other situations, a flat board or skid would have a horse or team of horses hitched to it; weight would be added, usually in the form of rocks, and the driver would urge his horses to pull the load, with more weight added as competitors were eliminated; the animals pulling the most weight or for the greatest distance were judged the strongest. These events became the formalized sport of horse pulling. In 1929 horse pulling events added tractor pulling.
In 1969, representatives from eight states congregated to create the National Tractor Pullers Association and a uniform book of rules to give the sport the much-needed structure. Tractor pulling is a motorsport competition which requires antique or modified tractors to pull a heavy drag (sled) along an 35-foot wide, 330-foot long track, with the winner being the tractor that pulls the drag (sled) the farthest. All tractors in their respective classes pull a set weight in the drag (sled). A tractor that pulls the weight the entire length of the track has completed a "full pull". Tractors that complete a full pull enter another round with more weight on the drag. The winner is the tractor that can pull the drag the farthest.
The drag is known as a weight transfer drag (sled). This means that, as the drag is pulled down the track, the weight is transferred (linked with gears to the drag’s wheels) from over the rear axles and towards the front of the drag. In front of the rear wheels, instead of front wheels, there is a "pan". This is essentially a metal plate, and as the weight moves toward it, the resistance between the pan and the ground builds. The farther the tractor pulls the drag, the more difficult it gets.
