California trainer Noble Threewitt, a figure of benevolence throughout his 75-year career, died Thursday at the age of 99.   Threewitt, who trained from 1932 until 2007, was known for his humanitarian work and leadership of the California Horsemen’s Benevolent and Protective Association. He served six terms as CHBPA president and was influential in the California Thoroughbred Horsemen’s Foundation. Both groups care for the needs of the backstretch workers.   Threewitt was married 77 years to his wife, Beryl, who died in July. As a trainer, Threewitt witnessed the opening of five major California racetracks – Santa Anita in 1934, Bay Meadows in 1934, Del Mar in 1937, Hollywood Park in 1938, and Golden Gate Fields in 1941.   The best horse Threewitt trained was Correlation, winner of the Florida Derby and Wood Memorial before finishing sixth in the 1954 Kentucky Derby. He also trained Devoted Brass, winner of the San Rafael and Swaps Stakes in 1993; Old Topper, a graded-stakes-winning sprinter in 1997 and 1998; and Theresa’s Tizzy, a graded-stakes-winning sprint mare in 2000.   At age 95, Threewitt on April 22, 2006 became the oldest trainer to win a race in North America when Threeatonce, owned by grandson Chris Chinnici, won a maiden race at Santa Anita. Threewitt officially retired Feb. 24, 2007, his 96th birthday. He won more than 2,000 races.   Threewitt was born Feb. 24, 1911 in Benton, Ill., grew up in a small Illinois town, was introduced to racing at a local fair, and rode briefly in Kansas City before he started a training career in 1932 at Agua Caliente in Tijuana, Mexico. Threewitt was on hand that year when Australian champion Phar Lap won the Agua Caliente Handicap.   A fixture in California for seven decades excluding a brief stint in the 1930s when he trained in New York, Threewitt won training titles at Hollywood Park in 1959, 1960 and 1961, and at Golden Gate Fields in 1970. In April 1954, he won with nine consecutive starters at Tanforan in San Bruno, California.   Threewitt died in an assisted living facility in West Covina, Calif., according to his family. In lieu of flowers, a donation may be made in Threewitt’s name to the California Thoroughbred Horsemen’s Foundation. Services will be private.