Six years ago, when Joe Klecker was named to the inaugural class of the On Athletics Club (OAC) in Boulder, Colorado, his goals were all about racing fast on the track. But based on his physiology, his tenacity, and even his genes, coach Dathan Ritzenhein already knew Klecker was destined to become a marathoner—and probably a very good one.

When the team now known as OAC Global formed in the summer of 2020, it featured eight postcollegiate runners chasing Olympic berths from 1,500 to 10,000 meters. The OAC sent several runners (including Klecker) to the Tokyo Olympics and brought home medals from Paris.

But track success was only the first step of what Ritzenhein envisioned. In the years since, he and coach Laura Thweatt have built an elite marathon program, too.

Kenyan great Hellen Obiri , four-time Major Marathon winner and current women’s New York City Marathon course record holder, put OAC on the marathon map after joining in 2022.…