Documentation for child traveling across USA/Canada border?

I am a Canadian citizen living in the USA waiting for my I-485 to be approved however I want to separate from my husband who is an American. We have an 18 month old who was born in the USA , wondering what type of documentation I would need to take her over the border without him. I would have his permission so whatever he would need to sign ect. I will be applying for her Canadian citizenship while in Canada based on birth abroad to Canadian citizen. Thank you for any information.

Her Original Birth Certificate as well get the letter from her father authorizing you to take the baby across the border notarized. It will have to state that yes you have his permission to take the baby into Canada permanently type thing. As well it would be a very good idea to get some legal separation papers with custody agreement before you travel.