David McNamara was a man who lost his wife, Molly, in a car accident on Highway 41.
David was married to Molly and one night, 15 years preceding the present, they had an accident on Highway 41 when their car hit and killed Jonah Greely. David survived but Molly didn't make it. David soon moved on and married again.
In 2007, Sam and Dean, posing as FBI agents to investigate yearly accidents on Highway 41 as a result of Molly and Greely's ghosts haunting it, interview David about where Molly was buried. David confirmed that Molly was cremated, complicating the Winchesters' hunt.
The morning after the 15th anniversary of the accident, David woke up to happily greet his second wife, unaware that the Winchesters had brought Molly's ghost to see him and convince her to let him go to move on.