What documents do I need when traveling with a baby without my Husband to Canada from US?

I would bring the baby's birth certificate, social security card if they have one, & passport if they have one. You can always call triple AAA

you only need babys birth certificate and a notarized
letter of concent from your husband to remove his son from the states.

Birth certificate, passport, social security card and a note from your husband that it is okay to travel with your infant. I just took this trip with my new husband and they asked me if it was okay to have the kids there without there father present. I gave them the note in which the signitures both matched and was able to travel with my kids and new infant.
Have a great trip

You require the child's passport (if he/she has one). If he/she doesn't have a passport, you require proof of the child's US citizenship, proof of parentage and a notarized statement of consent from your husband. The easiest things to use are either the child's US Birth Certificate (if born in the US) or the child's Consular Report of Birth Abroad (if born abroad) or the childs US Certificate of Citizenship, which show your name as the mother, aswell as the fathers name.

You do NOT need to take a Social Security card, it is not required, does not prove anything and is totally useless in this case.