It happened on Wednesday at 2:10 p.m.
Officers arrived in the 300 block of Glasgow Drive in the Glasgow Court Trailer Park to find a car seat on the sidewalk with an infant buckled into it.
A resident told police a woman wearing shorts and a multi-colored shirt was seen walking away from the baby.
Officers located the baby's mother, 24-year-old Abbie Arms, a short time later at her home in the 200 block of North Patrice Drive, which is located in the same trailer park.
Arms told police she had become distracted by a phone call and left her son.
Arms was charged with endangering the welfare of a child and released on $250 bail.
The baby is now in the custody of the Delaware Division of Family Services.
