The Chicago Marathon means business.

That’s how Ben Rosario sees it. Rosario, the head coach of the Northern Arizona Elite training group is sending two athletes to race in Chicago Sunday, and they are all going for the same reason.

“People go to run fast,” Rosario said over coffee in Flagstaff, Ariz., where his athletes live and train at 7,000 feet above sea level to maximize their oxygen-rich red blood cell levels.

Rosario, of course, was talking about the best marathoners in the country, some of whom are in his training group. But he could have been speaking for many of the thousands of lay runners who will toe the starting line Sunday, and thousands more who plan to run the race in the future.

The New York City Marathon has marketed itself as the world’s marathon, bringing in tens of thousands of international runners to the city’s biggest block party. The Boston Marathon has positioned itself as the most prestigious marathon in the world, a Super Bowl for amateur runners where meeting the race’s stringent qualifying standard provides a lifetime of bragging rights to runners of all ages. And the Chicago Marathon has become known as the racetrack — where runners go looking for their best performance.