Universally known by the nickname, "Buster," Millerick was born in Petaluma California and learned his trade at his cousins ranch in Sonoma Valley (Schellville Ca.] that today is known as the Larson Family Winery on Millerick Road. Owner Tom Larson is the great-grandson of Michael Millerick who bought the property in 1899. The Millerick family raised horses, ran the largest rodeo stock line in California and operated a [rodeo]]. Buster's uncles Tom, Jack and George also trained thoroughbred racehorses. 
Buster Millerick began working as a professional trainer while in his twenties and went on to a career that spanned more than half a century. Shortly after Santa Anita Park opened in Arcadia, California in 1934, Millerick was hired to condition horses for Charles Howard and would work under head trainer Tom Smith when the stable acquired the legendary Seabiscuit in 1936. In 1940, Millerick won his first important race for the Howard stable when Yankee Dandy captured the California Breeders' Champion Stakes.
A modest man, Buster Millerick avoided the limelight as much as possible. In a July 2005 story on Native Diver, the California Thoroughbred Breeders Association quotes stable owner and Millerick client Louis K. Shapiro as saying that "you never saw him [Millerick] in a winner's circle photograph." 
During his career, Buster Millerick trained a number of very good racehorses including DeCourcy Graham's Kissin' George and Verne Winchell's Champion filly, Mira Femme. However, he is by far best remembered as the trainer of Mr. & Mrs. Louis K. Shapiro's U.S. Racing Hall of Fame inductee, Native Diver. A gelding, Native Diver won thirty-four stakes races from age two through age eight, including an unprecedented three straight editions of the Hollywood Gold Cup, and was the first California-bred to earn a million dollars in racing.
After a short illness, Buster Millerick died at age eighty on September 30, 1986 at Methodist Hospital in Arcadia, California.