Follow up Question: Is this due to the northern boundary of Maine being disputed with Canada well into the 19th century? Or was it disputed because it wasn't heavily populated?

Upstate Maine is sparsely populated because it's very mountainous and the combination of soil and climate make it largely unsuited for growing most types of crops. Farms in this area typically produce potatoes or blueberries, and not much else. There's some diary farming, but poor transportation links to markets historically made it hard to export even processed dairy products like cheese.

Today, much of the land North of I-95 is commercial forest plots, mostly owned by the big paper companies.