Librarian of Congress James Billington said the recordings represent part of America's culture and history.
"As technology continually changes and formats become obsolete, we must ensure that our nation's aural legacy is protected," he said.
Curator Matthew Barton said U2's sound, though not explicitly religious, has influenced and been combined with Christian rock in some churches, including the song, "I Still Haven't Found What I'm Looking For."
In the decade earlier, it was Linda Ronstadt who helped define a musical era. She interpreted other people's compositions, crossed genres and sold millions of records. Ronstadt was a tastemaker, Barton said, choosing an eclectic mix of early rock and country music for "Heart Like a Wheel" that could evoke what was happening in 1974.
"You can hold up that album for someone. If you want to get an idea of what's happening, start here," he said.
Ronstadt, whose hits include "You're No Good" and "When Will I Be Loved," is being inducted into the Rock and Roll Hall of Fame on April 10. In an interview, she said she didn't think about making a hit album with "Heart Like a Wheel" and was naive about the business of music.
"In retrospect, I don't think I realized it at the time how precarious my situation was in terms of my career where if I hadn't had a success with that particular record, I think it would have been game over," she told The Associated Press.
Ronstadt said she was surprised to learn the album had been selected for safekeeping at the library, but that it's nice to have a distinction.
"I just wish I had done a little better job singing," she said. "If I listened to that record now, it would probably kill me. I never listen to my own stuff."
Being in the company of the Everly Brothers in the library's recording archive is a special thrill, she said. Ronstadt's hit "When Will I Be Loved" was written by Phil Everly.
"They were a huge influence on all of us," Ronstadt said. "They had a sound like no other and a way of crafting and weaving harmonies that was like nobody else could do."
Last year, Ronstadt revealed she's been diagnosed with Parkinson's disease. She said the progressive effects of the disease have taken away her singing, and she misses it.
"You wake up in the morning and go `Well, can I still walk? Does this leg work? Does that leg work?" Ronstadt said. "But something's going to get ya. So that got me."
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For the first time, the recordings being preserved this year also include extensive White House recordings, capturing the era of President Lyndon B. Johnson. The set includes 9,400 telephone conversations, 77 cabinet-room meetings totaling nearly 850 hours. Barton said the Johnson recordings represent a dramatic time in history and a colorful character.
"This was not a boring person," Barton said. "He was certainly very direct and very earthy but also very interesting."
