Conversation so far:
where was Mary Surratt buried?
The coffins were buried against the prison wall in shallow graves, just a few feet from the gallows.
what did she die of?
A corporal raced to the top of the gallows and cut down Atzerodt's body, which fell to the ground with a thud.
was Mary also sentenced to death?
As Surratt's body was cut loose, her head fell forward.

Question: what prison did this occur in?
Self-contained rewrite: what prison Mary Surratt sentenced to die occur in?