Question: are there always 20 horses in kentucky derby

Answer: No, The Kentucky Derby was first run at 1 1/2 miles (12 furlongs; 2.4 km) the same distance as the Epsom Derby. The distance was changed in 1896 to its current 1 1/4 miles (10 furlongs; 2 km). On May 17, 1875, in front of an estimated crowd of 10,000 people, a field of 15 three-year-old horses contested the first Derby. Under jockey Oliver Lewis, a colt named Aristides, who was trained by future Hall of Famer Ansel Williamson, won the inaugural Derby. Later that year, Lewis rode Aristides to a second-place finish in the Belmont Stakes.