What year was the first dirt bike race?

Answer 1

Motocross was first known as a British off-road event called Scrambles, which were themselves an evolution of Trials events popular in northern Britain. The first known Scramble took place at Camberley, Surrey in 1924. During the 1930s, the sport grew in popularity, especially in Britain where teams from BSA, Norton, Matchless, Rudge, and AJS competed in the events. Off-road bikes from that era differed little from those used on the street.
Motocross was first known as a British off-road event called Scrambles, which were themselves an evolution of Trials events popular in northern Britain. The first known Scramble took place at Camberley, Surrey in 1924.

Answer 2

In 1952 the FIM, motorcycling’s international governing body, created an individual European Championship using a 500cc engine displacement formula.