When Diane Crump died last week at the age of 77, the tributes and obituaries penned in her honor naturally led with the pioneering accomplishment that, more than five decades ago, she was the first woman to ride against men in a North American pari-mutuel horse race. Today, nearly 57 years from that landmark achievement, it can be difficult to grasp just how challenging and arduous a breakthrough that was. It wasn't, for example, just a matter of some trainer deciding, "This young lady can horseback a little bit. I...