The list below shows the leading sire of Thoroughbred racehorses in North America for each year since 1830. This is determined by the amount of prize money won by the sire's progeny during the year. It is restricted to stallions which are based in North America, but currently includes earnings from overseas races in Great Britain, Ireland, France, Italy, Germany and the United Arab Emirates as well as domestic earnings.
Prior to 2015, the Leading Sire Lists published by The Blood-Horse excluded earnings from Hong Kong and Japan due to the disparity in purses. Starting in 2015, earnings from Hong Kong and Japan are included on an adjusted basis.[1]