Jim McKay was the one who came up with the idea to have this stakes day:
https://en.wikipedia.org/wiki/Maryland_Million_Day
"Jim McKay Maryland Million Day is an annual day of stakes races thoroughbred horse races operated by Maryland Million Limited, a company formed in 1985."
“Jim McKay first conceived the idea of a day of races for Maryland-sired runners after attending the first Breeders' Cup in 1984.”
But he does have a stakes race named after him that is run on Preakness day. Ben's Cat has won it four times, the last being this year:
https://en.m.wikipedia.org/wiki/Jim_McKay_Turf_Sprint
I am surprised the race named for him isn't run on Millions Day, though.