[kabumpo]

As a family, they would be referred to as the Surratts, not the Surratt’s.
The apostrophe, indicating the possessive, would be used when referring to the Surratts’ house - after the S, because, again, the noun is plural.

[OldPossum]

Thanks for that post number 3. Very few Freepers seem to understand that the possessive of a proper noun is indicated by the apostrophe, followed by an “s” whereas the plural is indicated by an “s” (except in the circumstance you point out) and there is NO apostrophe.

But it seems to be a hopeless campaign.

[Conserev1]

Sharp eye but I guess you missed the author calling Mary Surratt a He! Mary Surratt continued to assert his innocence and at noon on July 6th was told she would be hanged the next day.