Your County Recorder should have a record of ownership. This is known as chain of title. Chain of title is a timeline of who has owned the property since, well forever. As for getting the paperwork, I would contact your local county recorder. Title, becuase it is public record, is recorded with your county clerk. This is the easiest way to demonstrate ownership, however I am operating off of the assumption that you had title recorded. If you took out financing for your home, this is almost a guarantee.

If title has not been recorded I would begin by demonstrating property tax payments for the last five years. Adverse possession takes five years (at least in CA, check state statute) and involves paying taxes on the property you are trying to acquire (among other things)... if you have been paying your property taxes, you're safe from adverse possession...