It was always going to be difficult to find a cover that would bring together the many diffuse strands of The Joshua Tree succinctly. Lyrically, the record was overflowing with powerful imagery. There were political and religious elements in the thematic mix. And musically, it was different to anything U2 had done before, with a far deeper connection to the blues, gospel, soul and folk music.

Not only that: the quality of the songs ensured that contemporary concerns in 1987 met abiding universal themes, in a way that resonated hugely. It was music that was both intimate and epic in its scope. Try putting that in a wrapper!

The images that eventually donned the front and back covers of U2’s fifth album did, indeed, match the weight of the music contained within. The cover of The Joshua Tree went on to become one of the most iconic in rock history, inspiring U2 fans from across the world to make pilgrimages to the location in Death Valley.

So how did four lads from Dublin find themselves out in the wilderness of California in the first place?

“We’d decided early on that we wanted to shoot in America,” Steve tells me. “Which was obviously a big change from the previous album covers, which were all shot in Dublin. We discussed ideas about where we could shoot and I went out a week earlier, to make a list of locations. So that’s what we based our journeys on. Then we went out with Anton Corbijn, our photographer, and shot in different places over a period of six days.

“At that stage, I already had an idea about the content of the album. The songs weren’t finalised, as such, because U2 are the type of band that will develop songs and change them as they work on them, but I had a pretty good sense of where they were going with the material and what they wanted to achieve, so I knew to try to find locations based on that.”

The mental image of the desert as a metaphor for a sense of ‘spiritual drought’ was key for the band. Lyrical motifs of deserts, dust and water permeate The Joshua Tree. This all helped Steve navigate the journey.

“The initial idea was to visit various places where civilisation had broken down or where nature and civilisation came into conflict with each other and became enmeshed,” he recalls. “The American desert was obviously a focal point. One of the locations we went to was a ghost town called Bodie in the Sierra Nevada (pictured above) which is now a national monument. It had been a mining town in the 1920s, but was now abandoned and completely consumed by nature. That produced a lot of really powerful imagery that eventually didn’t make it onto the album cover but was used on the tour programme after that. From there, we went on to places like Death Valley to try to capture the image we were after.”

Steve’s depiction of U2’s journey on the tour bus seems to rhyme with the themes of the album itself. It was a sometimes exhausting search for meaning and clarity in a dried-up landscape. Lacking a communal radio on the bus, hours were whiled away with individual members listening to cassette players or having long conversations, poring over ideas. With their heads already swimming with songs, U2 largely gave creative control of the cover to Anton and Steve.

“There’s been times in the past where I’ve tried to design an album cover while the band are preoccupied with making the music, so the cover art almost becomes secondary. Whereas on this occasion, they had a much clearer sense of the material they were working with and we were all focused on shooting the right cover. It was probably the most rewarding work I’ve ever done with the band.

“One day we were driving and Anton spotted this tree out in the distance, a single tree, which is odd because they tend to grow in numbers. It was just out there on its own and obviously stood out so starkly against the landscape. Anton had his panoramic camera and thought that the location could work. So that’s where we ended up shooting and that’s what went onto the back cover.”

It was then that the possibility of The Joshua Tree becoming the album title went from being an idea to a solid reality.

“The title originally came from the fact that we were shooting at the Joshua Tree National Park,” says the designer, the memories of 30 years ago coming back as clear as ever. “It was an idea that Anton had discussed with us the night we went out there. Bono decided it had relevance with the music they were making because Joshua trees basically only grow in California and Israel. So there’s a crossover with their American roots and also their religious roots. It kind of made perfect sense when we discovered it.”

The more they thought about it, the more they liked it. Joshua trees, according to Mormon legend, were named by early American settlers because the stretching branches reminded them of images of the prophet Joshua raising his hands in prayer. The name, and the associated images – the sombre faces of the band on the front cover, coupled with the lone Joshua Tree on the back – seemed to perfectly underpin what the album was all about.

“When I got home to Dublin I looked at all the contact sheets and all the material that was available from the shoot, then I made some of the initial decisions. We’d always explore several possibilities and nothing was ever set in stone. We had a few alternative options that were quickly narrowed down to something we felt was working. I’d always work hand in hand with Anton because as a photographer he had a large input into what would work and what wouldn’t. Then we’d all sit down to go over the options.”

How did the letterboxing of the cover with black bars come into play?

“I was thinking that this album was about the ‘cinematic America’, rather than simply being a mere snapshot of the country. Rattle And Hum was perhaps more of an American album in the conventional sense, whereas The Joshua Tree seems to run much deeper and its music spoke to a broader context and a broader sense of ‘America’. The predominant band that was talked about at the time in America was Guns N’ Roses. Long hair metal was what the emerging LA music scene was about. This was obviously very different from that and had a much wider reach. I think a lot of that came not just from the lyrics but from working with the likes of Daniel Lanois and Brian Eno. They were bringing a whole range of influences to the forefront.”

That wide reach has made The Joshua Tree’s songs pressing and relevant 30 years on, says Steve. In his opinion, the Joshua Tree Tour couldn’t come at a better time...

“This is the perfect time for the band to be touring this album again. It was done at a time when there was a lot of political turmoil in places like South and Central America. That turmoil has pretty much come full circle with recent events, so there are really good reasons for them to be doing this album. Songs like ‘Bullet The Blue Sky’ and ‘Mothers Of The Disappeared’ are political about the era they were written in, but they’re also ambiguous enough to fit into any period.”

This is something that every U2 fan can agree upon. But I think most will also agree that the cover itself is also ambiguous enough to fit into different times and locations. The image is one that can easily be transposed to a Middle Eastern warzone, a fertile landscape dried up by climate change, or post-nuclear wasteland.

In every instance, the meaning of the image remains the same: The Joshua Tree is about searching for spirituality in a place where it appears to have run dry.