Cox took an interest in
horse racing at 16, with storied horseman
Edward Geers as his idol. A 16-year-old Walter won his first race with May Morning, collecting one-third of a $15
purse. He began training horses at age 18 after a brief apprenticeship as a
stableboy and assistant. By then, he operated a stable of 30 horses in Nashua. He secured a notable Grand Circuit win with Prince of Orange in 1903 at
Empire City Race Track, earning $1,000. He returned to driving by December of that year.
Granite State Park He began operating a public stable out of
Dover, New Hampshire at 24. In 1907, he took over the lease of Granite State Park, a mile track in Dover, for his spring training grounds. His horses raced under the Christian Hill Stable banner, and he was assisted by Bert Yeaton. In 1914, Cox sold Peter Scott for $30,000 to trainer-driver Thomas W. Murphy, under whom the trotter won 17 of 18 races the next year. He transferred his training operations from Granite State Park to Laurel Hill Farm. He was the leading reinsman on the 1920 Grand Circuit. The Laurel Hall driver won his first Charter Oak Stake with Grey Worthy (by
Axworthy) at
Charter Oak Park in September 1921.
Good Time Stable At the end of 1921, he joined
William H. Cane's Good Time Stable at
Historic Track in
Goshen, New York. During the 1922 season on the Grand Circuit, he earned $59,468 in prize money. He finished as the top money-winning driver, finishing slightly ahead of Thomas W. Murphy. In the spring of 1927, he became trainer of Fireglow, owned by Vermont's William Bradford, with the goal of preparing the colt for the Hambletonian Stakes. Cox guided Fireglow to a
world record of 2:04 during the 1927
Kentucky Futurity.
1929 Hambletonian Stakes After taking the 1929 Kentucky Futurity in straight heats with Walter Dear, he went on to win the
Hambletonian Stakes in Lexington on October 8, 1929. Cox trained the first four finishers in the 1929 Hambletonian, with Walter Dear placing first, followed by stablemates Volomite, Sir Guy Mac, and Miss Woerner. He handled Walter Dear in each of its winning races, earning $57,000 and finishing as the leading reinsman that year. By 1930, he had spent more than 45 years training and driving harness horses, remaining active as a driver in major races even at age 60. He gave up driving around that time and focused exclusively on training. In 1933, his staff included Harry Stokes, Ted Horan, and Bert Yeaton. The veteran trainer retired in 1938. ==Personal life==