Sometime between 1861 and 1865.  The photograph shows a locomotive moving away from the roundhouse at the Orange &amp; Alexandria railroad yard in Alexandria, Virginia. The LOC photo information page says railroad signal lights are on the pole in foreground.  I think those are glass insulators for telegraph lines instead.
<p>I modified the original Library of Congress high resolution TIFF Photo using Photoshop (Unsharp Mask filter + Auto Levels adjust).
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No known restrictions to publication.
Ken Redmond
CC BY-SA 2.0
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