It's for this reason that I'm so excited about a new effort to digitize the archives of America's public radio and television stations. When its public-facing website launches in 2015, the American Archive of Public Broadcasting (AAPB) will hold digital files of 40,000 hours of footage and audio tape that contain the second half of the American 20th century as it unfolded. Among those 40,000 hours will be interviews recorded as African-Americans struggled to register to vote during the Freedom Summer; there will be the live speeches and press conferences of Robert F. Kennedy and Ronald Reagan; there will be entire episodes of public-media favorites like Mister Roger's Neighborhood and Julia Child's The French Chef.

There will be moments like this one, as Edward R. Murrow took to the air to premiere WNDT, which later became WNET (known more commonly as Channel 13), the first public television station broadcasting to the New York metropolitan area. As he welcomes viewers, Murrow (smoking!) emphasizes the pride and purpose of public broadcasting, values that still hold true today: "Upon these airwaves you will see no commercials," he says. "The only thing this channel will sell is the lure of learning."

Today, pieces of history like that are stored on audiotape and film at stations and other institutions around the country. But those materials are fragile.

"The scary thing about it is that they are on physical formats that are deteriorating," Karen Cariani, director of WGBH's library and archives told me. "Video tape and audiotape is not a stable format. After 40 or 50 years, they are disintegrating. And the information—pictures, sounds on that physical medium—is disappearing. Unlike a piece of paper or a photograph that might last 100 years, media formats are extremely fragile."

By digitizing these archives, Cariani hopes to keep them intact and available to students of history for years and years down the road. The digital preservation files the archive creates will be held at the Library of Congress. "They have told us that their mandate is to preserve that material for the life of the republic plus 500 years," Cariani says. "I don't know how they start that clock or how they do that, but that's what they told us and we decided that was long enough." (Of course, digital preservation has its own challenges, but Cariani prefers not to dwell on that: "I start feeling nauseous when I start thinking about how you actually assure digital preservation," she adds.)

The initial goal of 40,000 hours of digitized content will be pulled from 100 different stations across the country. That figure—40,000 hours—may seem daunting, but it's a tiny, tiny fraction of what's out there. To digitize more, the archive will need a new source of funding after its current $1 million, two-year grant from the Corporation for Public Broadcasting runs out.