Churchill Downs will host the 150th running of the Kentucky Derby on Saturday -- a milestone.First run in 1875, the Derby is North America's oldest continuously run horse race. However, according to curator of collections at the Kentucky Derby Museum, Jessica Whitehead, the race's roots go back much further to a man who was born before Kentucky was even a state. "The 12th Earl of Derby is basically the namesake of the British Epsom Derby, and the Epsom Derby is basically the Father race, the mother race of the Kentucky Derby," Whitehead said.The 12th Earl of Derby was the title of the 18th-century English Nobleman Edward Smith-Stanley, and the Epsom Derby is a horse race he is credited with creating. A portrait of the man hangs in the Kentucky Derby Museum.The Epsom Derby is said to have inspired Merriweather Lewis Clark to start the Kentucky Derby.According to Whitehead, aside from the name and some rules, many might struggle to see similarities between the two races."The Epsom Derby looks very different in terms of actually watching the race," Whitehead said. "However, the inspiration behind it and the rules are similar."According to Whitehead, Merriweather Lewis Clark used the word "Derby" in Recognition of the Epsom Derby.According Whitehead, there is a tale that suggests America's most famous horse race nearly had a very different name. "There is a racing legend that the Earl of Derby and his racing buddy Sir Charles Bunbury were having lunch and discussing this new race they would be starting at Epsom Downs over in England," Whitehead said. "There was a coin flip, and as the legend goes, thankfully, the Earl of Derby won because otherwise, we would call it the Kentucky Bunbury."The Epsom Derby is still run every year in England on the first Saturday in June, and the event regularly draws upwards of 100,000 spectators.