AND THEY'RE OFF...
By Princess Purple
The 2017 Kentucky Derby will be the 143rd running, and is set for Saturday, May 6, 2017 with a $2 million guaranteed purse.
A journalist from a 1901 Louisville Courier-Journal stated, "The seats in the grandstand were filled with gaily dressed women and men. The mass of green, pink, red, yellow, blue, all the colors of the rainbow, blending into one harmonious whole was as beautiful a sight as His Eminence in the lead." - https://en.wikipedia.org/wiki/Kentucky_Derby
The rules that guided so much of 20th century culture seemed to be thrown out the window in the mid-to late 1960s. Though the Derby was still viewed as a most respectable event and women continued to dress as such, a change had occurred. Now that Millionaires Row had opened, society women wore increasingly louder hats and took pride and enjoyment in selecting one. - https://www.kentuckyderby.com/history/fashion
So, in pursuit of his vision, Clark and his wife enlisted the ladies of Louisville to attend the races to picnic with friends. They knew that part of creating allure for the event would be positioning it as a fashion event — so the dress code required "full morning dress" for men and women from the start. - http://time.com/4317873/kentucky-derby-hat-history