Even before U2's The Joshua Tree arrived on March 9, 1987, it was clear something big was on the horizon.

The Irish band had been building buzz ever since its debut album, Boy, was released in 1980. They picked up more momentum with 1983's War, thanks to MTV's around-the-clock airings of videos from the album. By the time The Unforgettable Fire came out the following year, even U2's critics were aware the group was on the verge of a grand and defining statement.

And what a statement The Joshua Tree made. The band quickly graduated from theaters to sold-out stadiums. The album rocketed to No. 1 (their first on the U.S. chart); so did the first two singles – "With or Without You" and "I Still Haven't Found What I'm Looking For" – pulled from the record. By the end of the year, U2 were the biggest band in the world.

They wasted almost no time getting back into the studio after the world tour in support of The Unforgettable Fire. Sessions began in early 1986 at a massive house in their hometown of Dublin with producers Daniel Lanois and Brian Eno, both returning from The Unforgettable Fire, once again behind the boards.

Like with their previous album, The Joshua Tree was inspired by the band's obsession with America, which they were becoming increasingly more familiar with thanks to their extended tours across the nation, as well as their growing interest in roots music. But they went deeper this time, uncovering some of the darker spaces. They also wanted to capture the nation's vast landscapes in music. (The album was even called The Two Americas at one point, reflecting the divide the band saw between what they were told to believe about the country and what they actually saw.)

The famous cover photo, shot in the California desert, is a pretty neat summation of the record's contents. An outtake, "Drunk Chicken/America," found on the 20th-anniversary edition of the album, also explores the band's relationship with the country. Even though the 90-second Bono-read poem was written in 1956 by Allen Ginsberg, it's more pointed than almost anything the band wrote for the record.

Just like last time, they had hoped to channel the influence and ambience from their working environment – The Unforgettable Fire was partly recorded in a castle – onto their new album. They had also hoped to have the project wrapped up by mid-year and to have the album in stores by the end of 1986. That didn't happen.

Watch U2's Video for 'I Still Haven't Found What I'm Looking For'

Recording continued throughout the year, with Lanois working with the band for a couple weeks at a time, and then Eno working with the band for a couple weeks at a time. They hashed things out with jam sessions. They wrote as they recorded. They recorded most songs live. And they took a break to join the Amnesty International tour with Sting, Lou Reed and Peter Gabriel.

The shows invigorated U2, who now had enough songs to stitch together a double album, something they briefly considered until they narrowed it down to the 11-track version that was released. The songs bathed War's rousing exuberance in the atmospheric haze of The Unforgettable Fire. It was the best of both worlds, in a sense: anthem-sized audience pleasers paired with the moody art-rock that got them tons of critical acclaim.

The new songs were sad, desolate and heartbroken at times. Other times, they were uplifting, spiritual and hopeful. Increased political and social involvement, as well as the death of a close friend, helped shape the album's themes. It was about America, but it was bigger than that too. (As with their earlier albums, The Joshua Tree is filled with Biblical imagery and references.)

A year after they started work on the album, they finally – after some location changes and reworking of a handful of the songs – emerged with their tour de force. The Joshua Tree took U2 to a whole new level. From the shimmering intro of the Edge's guitar on "Where the Streets Have No Name," which opens the album, to the mournful hum that ends the closing "Mothers of the Disappeared," the LP unravels like a natural classic. Just like they planned.

There really was no doubt The Joshua Tree would be big. The question was just how big? Turns out massively big. The album shot to No. 1 throughout the world. (It was the first record to be released on LP, CD and cassette on the same day.) Hit singles piled up well into the next year. It won a Grammy for Album of the Year. And its songs rank among the greatest of U2's long career: "Where the Streets Have No Name," "I Still Haven't Found What I'm Looking For," "With or Without You," "Bullet the Blue Sly," "In God's Country."

The tour in support of the record made them even bigger. Bono became a new rock hero. They were among music's most politically passionate and socially conscious artists. And everything changed for the band, including how they moved forward: Achtung Baby, their next proper album following 1988's tour souvenir Rattle and Hum, was a total reinvention of their sound and style – a direct reaction to The Joshua Tree's immense success.

All these years later, the occasionally self-serious, often mesmerizing and always brilliant Joshua Tree stands as U2's masterpiece.

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