What you need is a thread on the ancestry forum.
There are tons of public records available even if your family doesn't have anything. If you know the name of an ancestor who was born before 1940, where they lived then, and their birth year, there's a very good chance you can trace your ancestry back to the Civil war using nothing but census records, and then look for civil war service records that match. It's much easier if you have access to the records on ancestry, but some people here have had good luck just based on what's available for free, and there are some people here who will do ancestry lookups. Ask, it can't hurt!