The Halloween Half Marathon, 10K, 5K and Fun Run, features Missouri's largest 10K race and attracts many of the region's elite runners, along with thousands of runners and walkers of all ages and abilities, who dress in costume and compete for fun. More than 7,000 participants are expected to compete for fun, cash prizes and pumpkin pies.The event also features a 1-Mile Fun Run that is popular with families.