Walking up to the outdoor sites at the Flight 93 National Memorial near Shanksville, Pa. last week I was not surprised to see signs saying that smoking, food, bikes or pets are not permitted.

The final resting place of the 40 passengers and crew of United Airlines Flight 93 that crashed there on September 11, 2001 should absolutely be a space that respects the sacrifice they made.

I was at the memorial taking pictures for upcoming Inquirer stories on the twentieth anniversary of the worst terrorist attack in U.S. History, and had just stepped into the gift stop at the entrance to the visitor center.

Photographing the video screen as it looped through announcements of upcoming events and the Sept. 11 observance, I froze as the image of a camera with a red slash mark through it flashed in my viewfinder.

Did the National Park Service really prohibit the taking of pictures? In a gift shop?

I felt exposed - caught in the act with my two big “professional” DSLRs - and quietly left to put them back in my car, wondering why the “No Photography” sign wasn’t posted along with the hamburger, bike, cigarette and dog sign at the entrance from the parking lot.

Returning to look at the exhibits I asked the ranger, “why no pictures?”

He explained that the Park Service did not own the copyright for some of the photos included in the permanent exhibit, so they couldn’t be copied. They didn’t want to label the individual images as such, so just thought it would be easier to post the “No Photography” signs throughout the building.

I was relieved to learn it was nothing against photographers. That we were still welcome there, to reflect on the day that would change America forever. And we were still free to capture our impressions, and share our experience on this hallowed ground.

Since 1998, a black-and-white photo has appeared every Monday in staff photographer Tom Gralish’s “Scene Through the Lens” photo column in The Inquirer’s local news section. Here are the most recent, in color:

» SEE MORE: Archived columns and Twenty years of a photo column