A Last Will & Testament can become a public record in some cases — but only if or when it is submitted to a Probate Court upon the death of the person making the Will.
Most probate courts do have some restrictions on access to filed documents, for privacy reasons. But the fact that the documents are filed with a public body (the probate court) does permit third parties to utilize court procedures to gain access to the documents so filed.
Each state (and sometimes each Probate Court) has different requirements to access filed documents. You must check state laws and with the Probate Court where your interest lies to determine those requirements.
To create a valid Will, see Standard Legal’s Last Will and Testament legal forms software page.