Upper right corner is a search box. When I type in "vital records Massachusetts" and select the "show only ebooks" option, I get back 626 available options.
Literally, what search terms you wish to use is up to you. You can use the state, the city/town, etc. Bear in mind... this will only give you books that have been physically scanned in and, in most cases, are older books that are no longer covered by copyright law due to their age.