Washington Township police made a traffic stop Friday night on US 33 near Lincoln Boulevard when they saw a vehicle driving erratically.
When they spoke with the driver, Kaylean Grago, 32, of Bellefontaine, they found her to be under the influence of drugs or alcohol.
A 5-year-old child was in the car during the traffic stop.
In a search of the vehicle, officers found samples of drugs that tested positive for crack cocaine.
Grago was lodged in Logan County Jail and charged with possession of drugs and child endangerment.