If you are working at a camp near the Canadian border, you may be required to travel into Canada as part of your job, or you may want to cross the border during your time off. In order for you to re-enter the USA and continue working on your J-1 Visa you must have your DS-2019 form validated for multiple entry. This means that once you are in the USA you must send your DS-2019 to your Program Sponsor to have it signed.
You should contact the Camp Leaders office in the USA to find out where you need to send it. It will be returned to you as quickly as possible.