Wikipedia:Today's featured article/January 13, 2017

The Jersey Act was a 1913 regulation by the British Jockey Club and the owners of the General Stud Book that prevented most American-bred Thoroughbred horses from registering with them. It was intended to halt the increasing importation of racehorses of possibly impure bloodlines after a series of bans on gambling by US states, including gambling on horse races. The loss of breeding records during the American Civil War and the late beginning of the registration of American Thoroughbreds led many in the British racing establishment to doubt that the American-bred horses were purebred. The Act prohibited the registration of horses unless all of their Thoroughbred ancestors had been registered. Despite protests from American breeders the regulation was in force until 1949. By then, ineligible horses were increasingly successful in races in Europe, British and Irish breeders had lost access to French Thoroughbreds during and after the Second World War, and any impure ancestors of the American bloodlines had receded far back in most horses' ancestry.