Have you done one of the Genealogy DNA tests? And joined the cousins matching project?

Ancestry points me to Filipstad and Karlstad, south central Sweden.
One Google search said those had been traditionally Finnish immigrants.

The name my Gr Grandfather went by in the US was Peterson. On his Marriage cert, he spelled it with two-'T's, Petterson. His wife Johnson, might have been Johanson.

I want to go to Filipstad and Karlstad, but I can't get any response from the local genealogy groups, and it is a dreadfully long trip from the airport cities Stockholm or Gothenburg, in case none of those is relevant!

With the DNA matching project, I have a dozen or so suggestions from Finland. Might be on next year's plans.