After two and a half years of planning, the Digital Public Library of America website will go live on Thursday at noon, becoming the first national digital library in the world.

Initially conceived during a conference at Harvard in October 2010, the DPLA initiative has attracted experts from all over the country in a joint effort to provide open access to the historical and cultural heritage of the United States.

Starting Thursday, about two million items, including books, pictures, manuscripts, and other materials, will be available for free to the general public.

“Thursday will mark the end of what you could call the embryonic phase of the DPLA,” said Robert C. Darnton ’60, member of the DPLA board and Harvard University librarian. “We are [now] up and running as an organization with a legal existence and a highly professionalized staff.”

Following the Boston bombings on Marathon Monday, the DPLA board decided to cancel the celebrations for the virtual launch, which were scheduled for April 18 and 19 at the Boston Public Library. Darnton said that the decision came as a sign of respect for the victims of Monday’s bombing.

“It didn’t seem appropriate to us to celebrate something like the launch of the DPLA at a moment when everyone is dumbfounded by the tragedy of the explosions at the marathon,” he said.

According to Darnton, the ceremony was also postponed because it was not clear whether the Boston Public Library, which was closed to the public on Monday afternoon because of its proximity to the site of the bombings, will reopen on time.

“It’s important I think to have the launch in the Boston Public Library for symbolic reasons,” Darnton said. “This was the first public library in the country.”

In a message posted on Tuesday afternoon on the DPLA website, DPLA Executive Director Dan Cohen said that the launch event will be rescheduled for the fall.

“It was the right decision to make,” said Director of the Harvard Open Access Project Peter Suber, who was planning to attend the ceremony.

The Harvard library system, as one of the DPLA’s content hubs, will make some of its collections accessible to the public through the new digital library. The around two million items that will be available on Thursday, however, are just the beginning of a more extensive national library.

“From that core, the DPLA will grow and grow,” Darnton said.

In spite of Thursday’s launch, increasing the content of the digital library will be a challenge, said David D. Weinberger, member of the DPLA Technical Workstream and co-director of the Harvard Law Library Digital Lab.

Under the current copyright laws, the DPLA can only publish works 70 years past the author’s death, which makes the bulk of the twentieth century production still unavailable. The staff of the DPLA, however, is working to overcome this obstacle.

At a Harvard Innovation Lab workshop last week, Weinberger proposed a strategy called “library license,” which would encourage authors to loan their digitized copies of their work to local public libraries after they go out of print.