HARRISBURG - A dispute over the rights to the images of the historic post office murals almost forced the State Museum of Pennsylvania to pull the plug on the "Common Canvas" exhibit.

In 2007, the museum informed the U.S. Postal Service that it would mount an exhibit featuring high-quality photographs of the New Deal-era murals of Pennsylvania.

"We thought they'd be excited and happy," museum director Jack Leighow said.

Instead, the exhibit touched off a skirmish between the Postal Service and the state over whether the artwork is in the public domain.

Leighow said it was ironic that the Postal Service, which was a full governmental agency when the murals were painted, would charge to produce an image of artwork created with tax dollars.

The Postal Service, which now operates without federal support, told the museum in a letter that it had the right to restrict access to its property.

It asked the museum to sign a multipage agreement to relinquish rights to the images, pay $300 per photo used, and take no more photos of the murals, Leighow said.

"We were afraid we would not be able to do the exhibit," said Leighow, who figured it could cost the museum $12,000.

A spokesman for the Postal Service, Ray Daiutolo Sr., wrote in an e-mail that the artwork was part of a private collection the service maintained.

"The Postal Service owns all the physical artwork in our facilities, including the New Deal-era murals," he wrote. "These works were copyrightable, and to the extent that these murals have retained their copyright status, the Postal Service owns that."

In December 2007, the Postal Service gave permission for the exhibit, but told the museum it could not shoot any more photos of the murals. Without a full collection of contemporary photos - including from Philadelphia post offices - the museum had to go to the National Archives and elsewhere for archival images.

For the museum, signing away the rights to the photos was about "the principle and the precedent," Leighow said.

"We came to the conclusion we did not want to sign it," he said. "We felt it was contrary to the spirit in which the artwork was created - that is, for citizens of the U.S."

Contact staff writer Amy Worden at 717-783-2584 or aworden@phillynews.com.