Who made the Sgt. Pepper album cover, and what was the process like?

Peter Blake, with help from his then-wife Jann Haworth, made the Sgt. Pepper cover. He was a British pop artist, and the Beatles wanted something that felt like a carnival parade. The cover is a collage of cardboard cutouts—everyone from Marilyn Monroe to Karl Marx—that took weeks to assemble. They had to get permission from every living person depicted (or their estates), which is why someone like Hitler was nixed for taste reasons. It’s still the gold standard for album art.