Is a passport needed

U.S. citizens and permanent residents DO NOT require a passport to enter Canada.

But you need one if you want to go home.

Identification requirements for U. S. citizens and permanent residents

If you are a U.S. citizen or permanent resident, you must carry proof of citizenship such as a passport, birth certificate, a certificate of citizenship or naturalization, a U.S. Permanent Resident Card, or a Certificate of Indian Status along with photo identification. If you are a U.S. permanent resident, ensure you carry proof of your status such as a U.S. Permanent Resident Card.

- Travellers - Visitors to Canada​

 

It is not quite this simple. People sometimes in error say you can't enter Canada with felony records. This not true all across the board. Check out this website about Canadian Deemed Rehabilitation.

 

Sometimes; they never even charge me.. lol

 

Speaking of last minute surprises…
U.S driver accidentally takes wrong turn, ends up arrested at border with massive bag of cash

 

Ask your company if they are paying the passport fee. If they are paying it, get one.