The oldest continually operating marathon is the Boston Marathon.  The 126th running of the Boston Marathon took place on Monday, April 18th.  This map of the  1,037 marathons by state, scheduled in the U.S. for 2022, is divided by the population. The resulting distribution indicates the upper Great Plains and Rocky Mountain states tend to host more marathons on a per-capita basis. The number of marathon race finishers, across the nation, has steadily increased over the past four decades from 25,000 to over a half million.