John Dohms was last seen walking northbound on Creek Road into White Clay Creek State Park around 3:00 p.m. on September 13th.
He was wearing a bright green button-down shirt, green socks, white tennis shoes and khaki shorts. He may have a set of binoculars in his possession and wears a Medic Alert bracelet on his left wrist.
Investigators previously said Dohms suffers from dementia.
Police are asking residents of northern Newark, Hockessin and southern Chester County, Pa., to check their sheds, outbuildings, cars, under decks or other places of shelter.
Dohms is known to frequent stores in and around Main Street, the Pomeroy Trail, city and state parkland off Paper Mill Road, and University facilities. He also frequents trails in and around White Clay Creek State Park.
The family has created a special Facebook page, https://www.facebook.com/HelpUsFindJohnDohms to aid in the search.
Anyone with information about his whereabouts should call 911 immediately.