What can we take in RV across the Canadian border??

Mr Biggles wrote:
Firewood is another item not to take across the border in either direction.

Correct. The dock at Port Angles often has a pile of firewood dropped by people when the workers for the Blackball tell them they cant take it with them.

In fact hauling firewood (none commercial, not heat treated, etc) between states is getting dicey. Many states have banned "importing" firewood from other states and some have restricted movement inside the state.