Those who watched Boston’s revered Fourth of July celebration Monday night on CBS were treated to spectacular views of fireworks exploding behind the State House, Quincy Market, and home plate at Fenway Park, among other places - great views, until you consider that they were physically impossible.

As viewers began to point out yesterday, it would not have been geographically possible to see the fireworks above and behind the landmarks in question, since the display was launched from a barge in the Charles River and in directions away from those places.

“According to CBS, you can see the fireworks from the right side of Quincy Market, even though Beacon Hill is in the way,’’ wrote “Kaz,’’ whose real name is Karl Clodfelter, a commenter on the Boston blog UniversalHub.com. “Also, they come up behind the State House when you’re standing across the road . . . which means the barge must have been parked on the Zakim this year,’’ wrote Clodfelter, a research scientist from Brighton.

David Mugar, the Boston-area businessman and philanthropist who has executive produced the show for nine years, confirmed yesterday that the footage was altered. He said this was the first year such alterations were made.

Mugar said the added images were above board because the show was entertainment and not news. He said it was no different than TV drama producer David E. Kelley using scenes from his native Boston in his show “Boston Legal’’ but shooting the bulk of each episode on a studio set in Hollywood.

“Absolutely, we’re proud to show scenes from our city,’’ Mugar said. “It’s often only shown in film or in sporting matches. We were able to highlight great places in Boston, historical places with direct ties to the Fourth. So we think it was a good thing.’’

A CBS Television spokesman declined comment about whether the network was aware of, or approved of, the fireworks show being digitally altered.

The footage of the landmarks was shot several weeks ago. According to Mugar, camera crews from Boston 4 Productions, the production wing of Boston 4 Celebrations Foundation, the fireworks show’s parent, crisscrossed Boston and Suffolk County shooting video of famous landmarks one evening in May.

“I’d say we shot from about 8 p.m. till 4 or 5 the next morning,’’ Mugar said. “Among other places, we got video of the Old North Church, the State House, Quincy Market, the statue of Paul Revere, Fenway Park, with the full cooperation of the Red Sox , who let us in and turned on certain lights for our shoot. And we did it all with the intention of superimposing the fireworks over the images. The technical process is called matting.’’