Last week's historical photo was the second in the series to come from the Library of Congress. The undated photo showed the inside of Bartram's Bridge. According to the LoC, which has many photos of the bridge and a historical narrative:

This simple covered bridge, erected in 1860, is one of the few covered bridges left in Chester County, and is the only one planned to preserve.

Commenter Eric Lewis wasted no time answering the question correctly. The same morning the photo was posted, he wrote:

Bartram's Covered Bridge, near intersection of Boot & Goshen in Newtown Square. 

http://goo.gl/maps/uHtrN 

http://www.historicnewtownsquare.org/historic-sites/bartrams-covered-bridge/

Rick Shouse seconded Eric's answer. Christine wondered if it was actually a bit farther north, as did Sharon Moran, Jill and Diana Genn. Christine wrote:

Or is it the covered bridge at Valley Forge Park? Yellow Springs Rd and Rte 252.

Susan was able to help point out why Valley Forge didn't quite fit the bill:

I'm deferring to you, Eric. The Knox bridge in Valley Forge was recently repainted and had a lot of wood siding replaced. Notice, too, that the planks on the floor of the Knox bridge run lengthwise, while the ones in the above photo run horizontally.

For more information on Bartram's Bridge and to view more historical photos, visit the Library of Congress.