The man, who now lives in Florida and was not identified, explained to police that he had left the box and the flag behind the house he was moving out of following a "bad divorce," Police Chief Sonny Bedsole told AL.com.
It was not clear how the items, which cops estimated to be at least a decade old, wound up in the ditch.
He was reportedly told about the ashes by friends, who read news stories about the discovery.
The discovery was made several weeks ago by workers off County Road 4 between Florala and Lockhart, near the state’s southern border with Florida, AL.com reported.
Cops received several tips after news of the discovery became public, but nothing connected the remains to its proper owners until now, they said.