Arlene Pieper became the first woman to officially finish a marathon in the United States when she finished the Pikes Peak Marathon in Manitou Springs, Colorado, in 1959. Her daughter Kathie, 9, became the youngest competitor at that time to finish the race to the summit, but did not finish the whole marathon. Arlene also entered the Pikes Peak Marathon in 1958 but stopped at the summit, therefore being disqualified. In 1959 women had the choice of a race to the summit or the full marathon up to the summit and down. That year Katherine Heard was first to the summit with a time of 5:17:52 but did not run down the mountain. Arlene reached the summit four minutes later, and finished the marathon with a time of 9:16.
She did the marathon to promote a gym she and her husband owned in Colorado Springs, called Arlene's Health Studio. She trained for a year, wearing tennis shoes she bought from a dime store. She had three children at the time. After spending four years in Colorado, she and her husband returned to California, where she had lived as a teenager and where they had run some gyms for exercise guru Harold Zinkin. They were also acquainted with exercise guru Jack LaLanne and Arnold Schwarzenegger. After they returned to California they ran another gym for Zinkin.
Pieper was unaware of the groundbreaking nature of her marathon until she was contacted by a historian in 2009. She served as the official starter for the Pikes Peak Marathon that year, and hung the Pikes Peak Marathon medal around the neck of the 2009 women's winner, who credited her win to Arlene's inspiration. As of 2014, Arlene attends the Pikes Peak Marathon every year as part of the ceremonies.
Pieper was named as one of the 2014 Heroes of Running by Runner's World.