The Asmussen Horse Center in Laredo, TX—built by Keith and Marilyn Asmussen thousands of miles from any Thoroughbred racing hub—is one of the country's most successful and renowned stable.  Top trainers and owners ship hundreds of their young horses there every year, confident they and their two sons will produce well-schooled 2-year-olds ready to run.  The heart of the operation is Keith Asmussen, a rawhide-tough native of South Dakota. Keith rode in his first Quarter Horse match race at nine.   His extraordinary talent with schooling young horses is why the center broke 250 yearlings last year.   The soul of the operation is Marilyn, a charismatic and equally competent horsewoman; she competed in rodeos while in high school.   In 1974 she became the first woman in New Mexico to hold a trainer's license, and for years conditioned the family's Quarter Horses while Keith raced them at tracks in Texas, New Mexico and Colorado.  They met when they were five; married in 1965 and began their 60+ year career with horses (which continues to this day).  The South Dakota winters caused them to move to Colleyville, Texas, then Oklahoma and finally Laredo, TX.  Soon their farm was breaking 100+ Quarter Horses.  Keith had mounts on several champions, including 1972 world champion Mr Jet Moore, and the Asmussens together campaigned champion 2-year-old gelding Vespero.   In the 1970s, they turned to Thoroughbreds and ultimately built their training center in 1984.  Their eldest son Cash  is  an  international champion jockey with more than 3,000 winners and career earnings of nearly $54 million.  Youngest son Steve is a highly sought-after horse trainer, with training titles at Texas' three major racetracks, Fair Grounds and Churchill Downs. His runners have earned more than $35.6 million.  The Asmussen center has produced six Eclipse winners; three Breeders' Cup winners; three Millionaires; 75 Graded Stakes winners and more than 200 Stakes winners. Other businesses include Asmussen Horse & Rider Equipment; El Primero Training Centre; KC Horse Transportation; Rio Grande Compost Company and Asmussen Blood Stock and Sales Company.  Though horse racing continues to be challenging, Marilyn states they feel blessed to do something they really love.