DULUTH, MN (KDAL) - Registration for Grandma's Marathon has been extended to June 7th. The 37th running of the event is being held on June 22nd. Since the marathon falls a week later than usual, Executive Director Scott Keenan says it's appropriate to give runners some extra time to commit to enter the race. Get more information and register online at GrandmasMarathon.com. More than 7100 have currently signed up to run Grandma's, the 14th largest marathon in the country.