Flights departing to the United States will clear U.S. Customs and Border Protection in Toronto. This means you arrive in the United States as a domestic passenger. The hours of operation for pre-clearance are 0330-2100 at Terminal 3 and 0430-2100 at Terminal 1. Should you have any questions related to travel into the United States (i.e. documentation/visa requirements, plant/animal or food restrictions) you may reach their Info Centre at 1-202-325-8000 or through the following link: https://help.cbp.gov/app/home/noIntercept/1