Phyllis Mills Wyeth, a noted philanthropist, conservationist, and breeder and owner of Thoroughbred racehorses, died at her Lookout Point Farm on the Pennsylvania-Delaware border Monday with her husband, famed painter Jamie Wyeth, at her side, according to the Longwood Funeral Home, in Kennett Square, Pa., which is handling the arrangements. Mills Wyeth, 78, was the daughter of the investment banker James P. Mills and Alice du Pont Mills. Born in New York City, she was raised at Burnt Hill Farm in Middleburg, Va., adjacent to her parent's Hickory Tree Farm, a Thoroughbred breeding and training facility. Her parents raced a number of top horses, including the Virginia-homebred Believe It, 1983 champion 2-year-old male Devil's Bag, and the $1.9 million yearling purchase Gone West. Mills Wyeth picked up her parents' love of Thoroughbreds and raced as Chadds Ford Stable. She bred and raced 2012 Belmont Stakes winner Union Rags and owned Dancing Rags, winner of the Grade 1 Alcibiades in 2016. Union Rags was a product of her parents' breeding program, with his female family tracing back four generations to Glad Rags II, winner of the English 1,000 Guineas in 1966. Tempo, the mare who produced Union Rags, was sired by Gone West. Mills Wyeth sold Union Rags for $145,000 as a yearling but came to regret the decision and bought him back as a 2-year-old for $390,000. Sent to trainer Michael Matz, he went on to win the Grade 2 Saratoga Special, Grade 1 Champagne, Grade 2 Fountain of Youth, and the Belmont. Union Rags is scheduled to stand the 2019 breeding season at Lane's End Farm for a fee of $60,000. Paralyzed at age 20 in an auto accident, Mills Wyeth's philanthropic causes included fighting for the rights of the handicapped and disabled, and helping the disadvantaged. She was an early patron of the Tri-County Conservancy, now the Brandywine Conservancy and Museum of Art, which protects scenic lands from development. Funeral services will be private. In lieu of flowers, donations may be made to the Brandywine Conservancy and Museum of Art and the Farnsworth Art Museum.