U2's 'The Joshua Tree' album turns 30

— -- U2's classic album, "The Joshua Tree," was released March 9, 1987 -- 30 years ago today. With over 25 million copies sold worldwide, "The Joshua Tree" is U2's best-selling album, and one of the best-selling albums of all time.

"The Joshua Tree" arrived three years after U2's 1984 album "The Unforgettable Fire," which saw the band experiment with ambient music.

With "The Joshua Tree," U2 explored Americana and Irish roots music for influences, while also diving more into the anthemic sound of "Pride (In the Name of Love)," one of its most popular songs.

Beginning with the opening track "Where the Streets Have No Name," U2 made its stadium aspirations clear. The song takes a long, fade-in intro as The Edge's main riff builds up to Bono's triumphant first lyrics: "I wanna run."

Following "Where the Streets Have No Name" on the track listing are two of U2's biggest hits: "I Still Haven't Found What I'm Looking For" and "With or Without You."

Both tracks reached number one on the Billboard Hot 100, and remain the only U2 songs to have achieved that feat.

To mark the 30th anniversary of "The Joshua Tree," U2 will embark on a North American tour this spring and summer, during which they'll be performing the album in its entirety. The tour, which kicks off May 12 in Vancouver, will make a stop at Bonnaroo, marking the first time U2 has headlined the Tennessee festival.

U2 will also be celebrating today with an online Q&A session on Facebook starting at 3 p.m. ET.