I'm preparing a blog post about immigrants from Tasov, Hodonín district, in Moravia - and I've accidentally bumped into one document I'd like to show to people who are interested in Czech genealogical research. It is "testimonium matrimonii contracti", which means testimony about contracting a marriage. Such documents were provided to people who wanted/needed to prove they were married.
My experience is not many people know that church records (which are usually not available online) contain much more information than marriage licences (which are often available online). So if your ancestors were married in U.S. and you don't know where they came from - don't forget marriage church records. :)