Brain Snacks: Tasty Tidbits of Knowledge
At the age of 71, Ambrose Bierce decided to travel to Mexico. The year was 1913 and the Mexican Revolution was in full swing. Bierce disappeared without a trace (source).
Owl Creek is real. It bordered the Shiloh (Tennessee) battlefield and is now a canal (source).
A soldier named John McCreath Farquhar fought for the Union in the Civil War and later became a member of Congress. Maybe Bierce heard the (weird) name and liked it.