The Grinnell Invitational has been held at Ahrens Park since I have been here (2005). I am uninformed prior to that point. The course was changed a bit in 2006 (primarily run in the opposite direction), but has remained the same since that time.
Here are full results of the Varsity Races for those interested:
http://pellacrosscountry.com/2013/09/grinnell-invitational-2013-boys-varsity-full-results/
http://pellacrosscountry.com/2013/09/grinnell-invitational-girls-full-results/