Mar-Kell was an American

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 Champion 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...

 filly

Filly

A filly is a young female horse too young to be called a mare. There are several specific definitions in use.*In most cases filly is a female horse under the age of four years old....

 racehorse

Horse racing

Horse racing is an equestrian sport that has a long history. Archaeological records indicate that horse racing occurred in ancient Babylon, Syria, and Egypt. Both chariot and mounted horse racing were events in the ancient Greek Olympics by 648 BC...

. Her dam was the 1934 American Champion Two-Year-Old Filly Nellie Flag

Nellie Flag

Nellie Flag was an American Thoroughbred 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 to win a stakes race....

, and her sire was the 1930 Epsom Derby

Epsom Derby

The Derby Stakes, popularly known as The Derby, internationally as the Epsom Derby, and under its present sponsor as the Investec Derby, is a Group 1 flat horse race in Great Britain open to three-year-old thoroughbred colts and fillies...

 winner Blenheim, who had been imported to the United States in 1937 by a syndicate that included Mar-Kell's breeder, 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...

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Mar-Kell was bred in Kentucky

Kentucky

The Commonwealth of Kentucky is a state located in the East Central United States of America. As classified by the United States Census Bureau, Kentucky is a Southern state, more specifically in the East South Central region. Kentucky is one of four U.S. states constituted as a commonwealth...

 and was raced by Calumet Farm for four yearsm from age two through five. Trained by future U.S. Racing Hall of Fame

National Museum of Racing and Hall of Fame

The National Museum of Racing and Hall of Fame was founded in 1950 in Saratoga Springs, New York, to honor the achievements of American thoroughbred race horses, jockeys, and trainers...

 inductee Ben Jones

Ben A. Jones

Benjamin Allyn Jones was a thoroughbred horse trainer.Born in Parnell, Missouri, Ben Jones went into the business of breeding and training of thoroughbreds during the first decade of the 20th century, racing his horses on small circuits in the American West and in Mexico...

, as a four-year-old, Mar-Kell's 1943 performances earned her American Champion Older Female Horse honors.

After she was retired to broodmare duty, of Mar-Kell's offspring her best known is the Calumet runner Mark-Ye-Well

Mark-Ye-Well

Mark-Ye-Well was an American Thoroughbred racehorse. Bred and raced by Calumet Farm, he was sired by their five-time North American Champion Sire, Bull Lea...

. Foaled in 1949, the colt had multiple wins in important stakes races including the Arlington Classic

Arlington Classic

The Arlington Classic Stakes is an American Thoroughbred horse race for 3-year-old horses held annually at the end of June at Arlington Park race track near Chicago, Illinois...

, American Derby

American Derby

The American Derby is a Thoroughbred horse race in the United States run annually at Arlington Park in Arlington Heights, Illinois. The inaugural American Derby was held at the city's old Washington Park race track and raced there until 1905 when the facility was closed and the track demolished....

, Lawrence Realization Stakes

Lawrence Realization Stakes

The Lawrence Realization Stakes was an American horse race first run on the turf in 1889. The race, for three-year-old Thoroughbred colts, geldings and fillies, was last run in 2005.-History:...

, and the Santa Anita Handicap

Santa Anita Handicap

The Santa Anita Handicap is an American Thoroughbred horse race held annually in early March at Santa Anita Park in Arcadia, California. It is a Grade I race for horses four years old and up , and is considered the most important race for older horses in North America during the winter racing season...

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Mar-Kell died in 1966 at age twenty-seven and was buried in the equine cemetery at Calumet Farm.