The title of "Best in Show" is given to the dog chosen as the winner of the Westminster Kennel Club Dog Show according to conformation show rules. It has its origins in the variety classes for champions that were introduced in 1905 which included prizes for best champion dog and best champion bitch. The title of Best in Show at Westminster has been awarded every year beginning in 1907 except for 1923 when changes in American Kennel Club rules prohibited mixed breed judging until a uniform process could be adopted; following further changes in rules it was awarded again in 1924.