Racing at Newmarket can be dated as far back as 1174, making it the earliest known racing venue of post-classical times. James I greatly expanded the sport's popularity from the early seventeenth century onwards. His son Charles I inaugurated the first cup race in 1634. Charles II was a regular presence and an enthusiast — he rode in races himself, earning the nickname "Old Rowley" after a celebrated stallion, a name now borne by the Rowley Mile racecourse. The Jockey Club, the governing body of British flat racing, has its clubhouse in Newmarket, though administration operates from London. The town's two racecourses — the Rowley Mile and the July Course — are separated by the Devil's Dyke, a remarkable Anglo-Saxon earthwork that runs for over seven miles across the chalk downland, beginning in Woodditton and ending in Reach.

Around 3,000 racehorses are stabled in and around Newmarket at any given time, trained by approximately 70 licensed trainers. The training grounds have three main areas: Racecourse Side, adjacent to the Rowley Mile; Warren Hill, which overlooks the town and includes three all-weather canters and numerous grass canters; and Bury Side, near the Bury Road and the railway line. All three areas are chalk downland, and the grassland has been cultivated over centuries to its current extraordinary quality. Special horse routes thread through the town so that horses can reach the gallops safely from their stables. Some of the world's most successful trainers are based here — Sir Michael Stoute, John Gosden, Saeed bin Suroor, Charlie Appleby — and the horses they train are worth, in many cases, between £5 million and £50 million each. The landscape around the town is dominated by over sixty thoroughbred breeding studs, including major global operations owned by Darley, Shadwell, and Juddmonte.

The history of Newmarket is wound tightly around English political history. In 1642, Charles I met a parliamentary deputation here that demanded his surrender of the armed forces. "By God not for an hour," Charles replied. "You have asked such of me that was never asked of a King!" The exchange effectively started the English Civil War. In June 1647, Charles was captured and brought to Newmarket as a prisoner, the whole of Cromwell's New Model Army keeping guard over the town. Newmarket had consistently Royalist sympathies. In 1648 there was serious fighting in the market place as the town attempted to rise for the King in the Second English Civil War. The palace James I built was largely demolished at the start of the nineteenth century — but a section survives and is now called Palace House, home to the National Horseracing Museum and Heritage Centre.

The statistics accumulate into something that reads almost like satire. Newmarket has a human population of around 16,000 and a racehorse population of around 3,500. Its two equine hospitals — the Newmarket Equine Hospital and Rossdales — are among the most advanced in the world. Its twin towns include Lexington, Kentucky, and Maisons-Laffitte in France — both of them also horse-racing centres. The town is the birthplace of William Thomas Tutte, a mathematician and World War II codebreaker; Thomas Elsdon Ashford, who won the Victoria Cross in the Second Anglo-Afghan War; and Dina Carroll, winner of a Brit Award. Newmarket sausages — produced here since the 1880s — hold a Protected Geographic Indication, and are given as a prize at the annual Newmarket Town Plate. The sport and the sausages are, in their own way, equally serious business here.