The Thoroughbred horse breed was developed in England specifically for horse racing in the late 17th and early 18th centuries. Three stallions were brought to England and bred to English mares that were a variety of breeds. We can trace all Thoroughbreds back to one of these sires.
The three stallions were named after the people who brought them to England and were: The Byerley Turk (named after Captain Robert Byerley), the Darley Arabian (named after Thomas Darley), and the Godolphin Arabian (named after the Second Earl of Godolphin).
Thoroughbreds are considered a hot-blooded breed, which means they are more spirited and are more suitable to experienced riders. They are best known for being great racehorses. With their athleticism and stamina, they are also used for show jumping, polo, dressage, and even trail riding.
They have used the Thoroughbred to improve other breeds including the Quarter Horse, the Standardbred, and possibly the Morgan.
A Thoroughbred holds the Guinness World Record for the highest race speed recorded over two furlongs (a quarter mile). The speed of 43.97 mph was achieved by a 2-year-old filly Thoroughbred named Winning Brew at the Penn National Race Course, Grantville, Pennsylvania, on May 14, 2008.
Also from Guinness World Records: The highest price paid for a Thoroughbred racehorse at public auction is $16 million for a two-year-old, then unnamed colt, who had yet to even race.
Here is a book about the famous Thoroughbred racehorse Northern Dancer: