The History and Significance of Del Mar’s Premier Race   The Pacific Classic, a jewel in the crown of the North American horse racing schedule, stands as the marquee event of the Del Mar summer meet. Run at 1 1/4 miles on the main track, this Grade 1 stakes race for three-year-olds and up offers a rich purse and a coveted "Win and You're In" spot for the Breeders' Cup Classic, which this year will take place at Del Mar.