This is an interesting image that features civil war era transportation and infrastructure. The bridge that connected Berlin, Maryland with the Virginia shore was destroyed by the Confederates in June 1861. Two parallel pontoon bridges have been assembled for the Union army to use in crossing the Potomac. In the foreground are supply wagons of the Army of the Potomac. The horizontal trace just behind the tents is a train that was in motion on the Baltimore & Ohio Railroad, I believe, during the exposure of the film for this photo. On the left are several stationary boxcars, probably on a siding. On the other side of the railroad tracks are more supply wagons and past them is the Baltimore & Ohio Canal.
The photograph is by Alexander Gardner at Berlin, – now Brunswick – Maryland. This is a cropped portion of the original image.