The Dutch have a tradition of exceptional harness horses. Traditionally, they were versatile horses, strong enough for farm work and elegant enough to take the family on outings or to compete. Since WWII and the decline of farm horses, they are now bred for sport. The breed was refined with an infusion of Hackney and American Saddlebred. Breed standards are very strict and the population is small. Like so many European Warmblood breeds, breeding stock goes through very strict testing in order to be registered. This ensures very high quality and exceptional health.
In the USA, they are crossed with Arabians to create a larger "Park" horse than the Saddlebred or Tennesse Walker.
A recent article in the Wall Street Journal described the economic woes of the Amish. The Amish benefitted during the recent contruction and housing boom. They used the extra income to purchase some luxuries, including fancy carriages (with LED lighting!) and Dutch Harness Horses. It was the Cadillac Escalade of the Amish world.
(click to enlarge)