The 2-year-old's grandmother was watching the girl when the child slipped away.
The girl crossed Route 20 and the Passaic River on railroad tracks that are used by freight trains before reaching Elmwood Park.
That's where Victor and Maria Cortez spotted the child on Monday night.
She tells the Herald News of West Paterson her husband called 911 and she approached the child, who started crying.
The girl could not tell police her name or where she lived.
She was reunited with her family after they called police when they realized she was missing.
No charges were filed.
Information from: The Record of Bergen County, http://www.northjersey.com
