Noah Armstrong established Doncaster Stable in Twin Bridges to take advantage of the Jefferson River Valley's ample water and rich soil. Armstrong firmly believed that Montana’s high altitude would give his racehorses great lung capacity and endurance. The large, round, three-story barn was completed in 1882. Architecturally stunning with vertical board and batten siding, ornamental window detailing, and an elegant primary entry, it was also technologically advanced. On the first floor, eighteen well-lit stalls around the outer edge allowed the horses to see each other and also gave them outside access to individual pie-shaped paddocks. Outside, there was an oval training track. The main entry could accommodate a ten-horse wagon laden with hay. The second level stored 12,000 bushels of grain and fifty tons of hay while the third floor housed Armstrong’s innovative windmill-driven water system. The barn was the birthplace of Spokane, the only Montana-born horse to win the Kentucky Derby. In 1889 Spokane won the fifteenth Kentucky Derby with a time of 2:34:50. This record time cannot be broken since the track was shortened from 1.5 to 1.25 miles in 1896. Despite the success of his horses, financial reverses during the Silver Panic of 1893 ended Armstrong’s horse breeding. When the property sold to Max Lauterbach in 1900, the ranch shifted from horses to cattle. After 1933, owner Arthur Bayers used the Doncaster Barn for many years as a sale barn for prize Hereford bulls. In 1997, it became part of the Hamilton Ranch.