Greyhounds have been used for hunting and coursing in the Middle East and Europe for at least 5,000 years, but it was not until the 1930's that dog racing became a commercial enterprise in America. That decade and the next five saw an explosion in the number of racetracks nationwide, as patrons were drawn in by the combination of gambling and the seemingly harmless spectacle of beautiful dogs out for a run. In the 1920's the International Greyhound Racing Association, an industry organization, was formed to regulate dog racing and try to control industry corruption. Its modern successor is the National Greyhound Association. 1961 Encyclopedia Britannica on greyhounds and greyhound racing
Dog racing reached its peak in the 1980s. Since then, growing public awareness of the cruelty of dog racing and competition from other forms of gambling has steadily undermined racetrack patronage.
Commercial dog tracks are dying across the country, but continue to survive in part due to tax breaks and handouts received from sympathetic politicians
Read more about the history
of greyhound racing here.