Nellie Flag was an American Thoroughbred

Thoroughbred

The Thoroughbred is a horse breed best known for its use in horse racing. Although the word thoroughbred is sometimes used to refer to any breed of purebred horse, it technically refers only to the Thoroughbred breed...

 racehorse who was voted the American Champion Two-Year-Old Filly of 1934. She was the first horse bred by Warren Wright's Calumet Farm

Calumet Farm

Calumet Farm is a Thoroughbred breeding and training farm established in 1924 in Lexington, Kentucky, United States by William Monroe Wright, founding owner of the Calumet Baking Powder Company. Calumet is located in the heart of Lexington's blue grass country, the finest horse breeding region in...

 to win a stakes race

Graded stakes race

A graded stakes race is a term applied since 1973 by the American Graded Stakes Committee of the Thoroughbred Owners and Breeders Association to thoroughbred horse races in the United States and Canada to describe races that derive their name from the stake, or entry fee, owners must pay...

.

An early favorite, Nellie Flag finished fourth in the 1935 Kentucky Derby

Kentucky Derby

The Kentucky Derby is a Grade I stakes race for three-year-old Thoroughbred horses, held annually in Louisville, Kentucky, United States on the first Saturday in May, capping the two-week-long Kentucky Derby Festival. The race is one and a quarter mile at Churchill Downs. Colts and geldings carry...

  and seventh in the Preakness Stakes

Preakness Stakes

The Preakness Stakes is an American flat Thoroughbred horse race for three-year-olds held on the third Saturday in May each year at Pimlico Race Course in Baltimore, Maryland. It is a Grade I race run over a distance of 9.5 furlongs on dirt. Colts and geldings carry 126 pounds ; fillies 121 lb...

, the latter a race won by her dam in 1924. Following an injury, Nellie Flag was retired in mid July of 1935 and stood at Calumet Farm as a broodmare where she died in 1953 at age twenty-one. She produced ten foals of which nine raced. Among her best were:

• Mar-Kell
  Mar-Kell
  Mar-Kell was an American Champion Thoroughbred filly racehorse. Her dam was the 1934 American Champion Two-Year-Old Filly Nellie Flag, and her sire was the 1930 Epsom Derby winner Blenheim, who had been imported to the United States in 1937 by a syndicate that included Mar-Kell's breeder, Calumet...
  
   (born 1939) - American Champion Older Female Horse (1943)
• Nellie L.
  Nellie L.
  Nellie L. was an American Thoroughbred filly racehorse bred and raced by Calumet Farm. She was sired by Blenheim II and out of the mare Nellie Flag....
  
   (born 1940) - won 1943 Kentucky Oaks
  Kentucky Oaks
  The Kentucky Oaks is a Grade I stakes race for three-year-old Thoroughbred fillies staged annually in Louisville, Kentucky, United States. The race currently covers 1⅛ miles at Churchill Downs; the horses carry 121 pounds . The Kentucky Oaks is held on the Friday before the Kentucky Derby each year...
  
  , Acorn Stakes
  Acorn Stakes
  The Acorn Stakes is an American Grade I race at Belmont Park in Elmont, New York for three-year-old Thoroughbred fillies. It is raced on dirt over a distance of one mile with a current purse of $250,000. It is the first leg of the US Triple Tiara and is followed by the Coaching Club American Oaks...
  
  
• Sunshine Nell (born 1948) - multiple stakes wins including Barbara Fritchie Handicap
  Barbara Fritchie Handicap
  The Barbara Fritchie Handicap is an American race for Thoroughbred horses run at Laurel Park Racecourse in Laurel, Maryland each year. A Grade II, this race is open to fillies and mares, age three and up, willing to race seven furlongs on the dirt and offers a purse of $300,000.The race is run in...
  
  , Autumn Days Handicap, Top Flight Handicap
  Top Flight Handicap
  The Top Flight Handicap is an American Thoroughbred horse race run annually at Aqueduct Racetrack in Queens, New York. The Grade II event is run in late November and is open to fillies and mares, age three and older...