I was surprised when I traveled there and met a an employee at Mount Washington that speaks french.

There was a huge wave of french Canadian immigration to the USA in the early 20th century, in part because work was scarce in Quebec and in part because of the effort to erase them from the map in the other provinces, many came back eventually, but many families decided to stay and they continued speaking french at home. Outside of them, the french speaking diaspora isn't big enough/doesn't renew itself, so there's no pressure for english speakers to learn it.