A family dog is being credited with protecting a young North Dakota boy after the three-year-old wandered away from his rural home.

Carson Urness was discovered missing from the family farm Monday evening, which prompted an expansive search that involved more than 200 volunteers combing 2,000 acres of land.

The seven-hour search involved the use of ATVs, a police aircraft and dozens of volunteers that searched the area on foot.

When rain began to fall around 2 a.m., authorities sent the volunteers home, but not before one volunteer spotted Cooper, the family's dog.

Cooper had kept Carson warm throughout the hours-long ordeal, officials reported, laying on top of the toddler who was found about a kilometre away from the family's home.

The golden retriever / German Shepherd mix kept Carson's body warm and dry as temperatures dropped.

Caron's mom Courtney Urness admitted that as the search went on it was hard not to think the worse. But she said was comforted knowing that Cooper was missing too.

"If anybody was going to find him, they would have to find Cooper," she told local media.

The Urness family said they found Cooper when he was a puppy on the side of a road.