These old Civil War photos of Alexandria are amazing. This one shows the steam frigate Pensacola in 1861, the beginning of the war. Click on it for some incredible details.
Alexandria, Va. Steam frigate Pensacola. Photographs of the Federal Navy, and seaborne expeditions against the Atlantic Coast of the Confederacy — the Federal Navy, 1861-1865.
Source: Library of Congress
We also came across some amazing old photos of the frigate here.