Canada

From the article in my OP:

"People often associate slavery with thousands of people working on a plantation.

It did not happen in Canada in the same way because of the climate and seasonal shifts that could not sustain year-round agriculture.

Nelson said enslaved people in Canada might well have harvested apples or corn, but they were also forced to milk cows, groom horses, and in the case of women, breastfeed the children of their white owners, to the detriment of their own children."

As to the economic benefits, well, again it was farms with slaves that benefitted economically just as it was the cotton plantations in the Southern US that benefitted economically.