The race is open to fillies and mares age four years old and up and is run at one mile (eight furlongs) on the dirt.
The race was named in honor of Nellie Morse, the last filly to win the Preakness Stakes (prior to Rachel Alexandra in 2009) in 1924.
Her daughter Nellie Flag was named two-year-old champion in 1934 and was the morning line and post time favorite in the 1935 Kentucky Derby (she finished fourth).
Nellie Flag also raced in the Preakness Stakes but finished seventh.
Nellie Morse's descendants, through Nellie Flag, include horse of the Year Forego, Kentucky Derby winner and champion three-year-old Bold Forbes, and champion handicap mare Mar-Kell.