Her sire was the great Tim Tam, by Tom Fool out of Two Lea. Many consider Tim Tam's loss of Thoroughbred racing's American Triple Crown only a matter of fate. After winning the first two legs (Kentucky Derby and Preakness Stakes), he was leading in the Belmont Stakes when he broke down, coming in second. Retired early, he went on as a sire, producing a number of stakes winners. Tosmah is considered his very best. Her dam, Cosmah, was the 1974 Kentucky Broodmare of the Year, who also produced Halo, who sired Sunny's Halo and Sunday Silence.
Tim Tam and Cosmah's daughter raced for four years—1963 to 1966.
At the age of two, she started eight times and lost only once. For this, she was named the American Champion Two-Year-Old Filly of 1963. (This was before the Eclipse Awards when championships were determined by the Daily Racing Form and the Thoroughbred Racing Association. More than once, these two bodies voted for different horses. In Tosmah's second year the Daily Racing Form considered her the best filly, while the TRA voted for Castle Forbes.)
When Tosmah was three, she started in fourteen races, winning ten, vying all year with a splendid filly called Old Hat. 1964 saw her highest earnings, $305,283, and two more championships: American Champion Three-Year-Old Filly and American Champion Older Female Horse, the latter title shared with Old Hat.
In 1965, at the age of four she won her second Maskette Handicap (now known as the Go For Wand Handicap) under 128 pounds, in the process beating the great filly Affectionately, no. 81 in the Blood-Horse magazine List of the Top 100 U.S. Racehorses of the 20th Century, in a driving finish.
As a broodmare
Of four foals, Tosmah gave birth to only one stakes winner, La Guidecca.
She died in 1992 and is buried at Briardale Farm, Estell Manor, New Jersey.
Tosmah was inducted into the Hall of Fame in 1984.
- "Champions, The Lives, Times, and Past Performances of America's Greatest Thoroughbreds, Revised Edition, Champions from 1893-2004," the Daily Racing Form