The site marks the old Garrett farm where Booth was surrounded by Union troops and burned to death when the farm was lit on fire.  

John Wilkes Booth

John Wilkes Booth (May 10, 1838 – April 26, 1865) was a famous American stage actor who assassinated President Abraham Lincoln at Ford's Theatre, in Washington, D.C., on April 14, 1865. Booth was a member of the prominent 19th century Booth theatrical family from Maryland and, by the 1860s, was a well-known actor.

• http://en.wikipedia.org/wiki/John Wilkes Booth