Slovaks can be found, for the most part, in a band which stretches from the Ohio Great Lakes east through Pennsylvania and parts of New York State.
Not particularly plentiful, and largely absent from much of the country, I decided to break with tradition and crop the Slovak map just a bit to make it easier to see the spots where they settled. The map isn’t perfect – one flaw is that I would need to make the coloration layer transparent if I wanted to allow city names and so forth to come through – but doing so makes it more difficult to spot the ethnic density coloration, so I’ve resisted the temptation up to this point. Try the Tableau tool so you can mouse over spots and get geographic information.
Link to Tableau tool: