Nothing is known of the mile marker's history before the outbreak.
In a flashback to shortly after the outbreak began, Martha and Hank have been involved in a car accident where their car hit a guardrail and Hank got impaled upon it. Martha desperately tries to flag down passing cars, but no one stops to help and Hank dies of his injuries, reanimates and has to be put down by Martha. Martha buries Hank under a tree nearby and spends several days at his graveside, slowly going insane from her grief and anger over people refusing to help them out.
Arriving at the mile marker, Morgan finds the remains of Martha and Hank's car and a police car that Martha stole with a zombified Jim Brauer in the backseat. Morgan sadly removes his friend from the police car and puts Jim down with his staff before finding Martha nearby at Hank's grave. Over Martha's protests due to her wish to die at Hank's grave and reanimate, Morgan drags her into the police car and sets out to reunite with his friends.
- The episode "MM 54" is named after the abbreviation for this location.