The easiest way to determine whether you are watching a contest between Standardbreds and Thoroughbreds is to look at the rider. Standardbreds and Thoroughbreds share a common heritage. An English Thoroughbred named Messenger was brought to the United States in the late 1780s and was the great-grandsire of Hambletonian, the American horse to whom every Standardbred can trace its lineage. Over time, a breed emerged, based not on genetics but on performance. Horses that were speedy like Thoroughbreds but were also rugged and had a steady gait developed into a new, American breed.
Most harness racing horses are pacers.
Most of these top races are held within a few hours' drive from Maryland. In its earliest days, men raced their Standardbreds along roads. Soon, they were racing Standardbreds in harness races at county fairs, traveling from fairground to fairground. After 1940, when pari-mutuel racing began at Roosevelt Raceway in New York, people began to race for purse money as well as the satisfaction of racing. The Maryland Standardbred industry began in 1947, when the State Legislature allowed pari-mutuel betting on Standardbreds.