A 1-year-old boy was found on the side of a busy San Benito road on Sunday evening.
A woman who was driving on U.S. Hwy 281 noticed the child, stopped her car to pick him up and called authorities.
A Cameron County Sheriff Deputy responded to the scene at 7:45 p.m.
She told the deputy that she feared the baby was going to be run over because of the 60 mph speed limit.
She also said that after picking the child up, the mother of the 1-year-old arrived six minutes later.
The mother, Aleda Girar, said she had put her son down on the living room floor so she could wash a baby bottle.
When she came back to the living room, she noticed he was missing.
Girar said the front door had been left open and when she went outside to look for her child, she saw the woman holding him.
The 34-year-old mother was arrested and charged with endangering a child with criminal negligence.
She appeared before Cameron County Magistrate Court Judge Luis Saenz where she was issued a $15,000 bond.