“Abbey Road” marked the end of an era when it was released on Sept. 26, 1969, as the last album recorded by the Beatles. (“Let It Be” would be the final LP released by the Fab Four.)

Here’s a look back, track by track, at the album that led to the Beatles’ breakup in 1970.

“Come Together”

The classic opening track, written by John Lennon, was originally conceived as an anthem for Timothy Leary’s 1969 campaign for governor of California, a race he lost to Ronald Reagan.

“The theme of the campaign was ‘Come together, join the party,’” says Kenneth Womack, author of the upcoming book “Solid State: The Story of Abbey Road and the End of the Beatles,” out Oct. 15. “It was really John who agreed to help out Timothy Leary, and then, of course, John realized, ‘Wait a minute, I got a great song on my hands here! Tim can forget about it.’”

The song also nods to a certain ’50s rock god. “Lennon apparently wrote it as a Chuck Berry-type song, with a Chuck Berry riff and some lines from [his 1956 single] ‘You Can’t Catch Me,’” says Bill Flanagan, co-host of “The Fab Forum” on SiriusXM’s The Beatles Channel.

“And I think it was [Paul] McCartney and Ringo [Starr] who slowed it down … It’s the furthest thing in the world from a fast Chuck Berry song now.”

“Something”

Frank Sinatra once described this George Harrison composition as “the greatest love song of the past 50 years.” But the tune also hints that it wasn’t all love among the Beatles at the time.

“It’s haunting; it’s not all romance,” Womack says. “There’s some darkness behind it, which, of course, was real. The band obviously was struggling. You can also hear a sense of nostalgia. They were certainly growing nostalgic at that time about their days together, which were running shorter.”

“Maxwell’s Silver Hammer”

Lennon was famously not a fan of this McCartney tune. “John made no secret about how much he struggled with hearing that song in any form,” says Womack.

And the painstaking process of making it certainly didn’t help the song score points with any of the Beatles. “I think they did dozens of takes of it … with Paul going, ‘Nope, do it again!’” says Flanagan. “So I think by the end, the other guys didn’t really like ‘Maxwell’s Silver Hammer.’”

“Oh! Darling”

Like “Maxwell’s Silver Hammer,” this ’50s throwback didn’t come easily. “Paul would come in every day, and first thing in the studio he would belt out that lead vocal to see if he got it right,” says Womack. “And it took several days, but he finally got the vocal that he wanted.”

But, Womack says, one of the Fab Four wasn’t exactly impressed with Sir Paul’s efforts: “Lennon, of course, rather ungraciously said, ‘Well, I think I sing that kind of song better than Paul.’ ”

“Octopus’s Garden”

Womack calls this fantastical sea voyage “Ringo’s last great moment with the band … one of his most original original compositions.” But the way that the song came about wasn’t so dreamy.

“He wrote it on Peter Sellers’ yacht in 1968 during the famous moment when he quit the band for a few days,” says Womack.

Adds Flanagan, “The guy running the boat told him, ‘Yeah, down there, octopuses gather shells and shiny things and make little gardens for themselves.’ He thought that was the most beautiful, peaceful thing in the world.”

“I Want You (She’s So Heavy)”

Side 1 of the “Abbey Road” vinyl LP ends with this track, which was the first one the Beatles worked on for the album.

Flanagan says that the song definitely lived up to the “heavy” in its title.

“It isn’t heavy metal, but it’s kind of heavy blues, which was a prevailing thing at that time with Cream and [Jimi] Hendrix and stuff,” he says.

“Here Comes the Sun”

The most downloaded and most streamed Beatles song of the 21st century didn’t come from the sunniest of places.

“That’s a song written when the Beatles were not getting along,” Flanagan says. “So George played hooky and went over to Eric Clapton’s house. He borrows one of Eric’s guitars and walks out in the garden and starts singing, ‘Here Comes the Sun.’”

“Because”

Beatles producer George Martin played the keys on this track. “And though [Martin] was an exquisite keyboard player, he had terrible rhythm,” Womack says, “so Ringo tapped out the downbeat for him so George Martin could stay in beat on that song.”

“You Never Give Me Your Money”

This track, which Womack considers the start of the medley that makes up the rest of Side 2, references the Beatles’ issues with their label, Apple Records. But the song also has an interesting musical twist. “You have the last use of George Martin’s famous wind-up piano technique,” says Womack. “They recorded it at half speed, and then sped it up [so] it has a kind of boogie woogie sound to it.”

“Sun King”

“It’s the Beatles’ plagiarism,” Womack says. “They’re borrowing heavily from Fleetwood Mac’s instrumental hit ‘Albatross’ and creating that beautiful ambience, a kind of … calming sound.”

“Mean Mr. Mustard”

This character, along with “Polythene Pam” in the following track, is based on a real-life person. “Mean Mr. Mustard was very likely this vagrant that John would see on the streets outside of London,” says Womack.

“Polythene Pam”

In real life, Polythene Pam was Polythene Pat, explains Womack, but Lennon changed the name because he thought it sounded better. “Polythene Pam was this kind of twisted woman that he had met many years before, and she liked to dress with plastic bags,” he says.

“She Came in Through the Bathroom Window”

“It’s apparently based on a true story,” says Flanagan. “The girls that hung around McCartney’s house trying to get a glimpse of him, one of them managed to come in through the window in his bathroom.”

“Golden Slumbers”

McCartney, who doesn’t read music, came across a piano songbook with “Cradle Song,” a lullaby by the English playwright Thomas Dekker. Then he made up his own music to go with the lyrics, resulting in “Golden Slumbers.” “He made it something even better than what it was,” Flanagan says.

“Carry That Weight”

Flanagan says this track plays like “an answer to ‘I Want You (She’s So Heavy).’ ” You can hear the end of the Beatles coming in McCartney’s confessional lyrics, says Womack: “It’s really about the Beatles and their difficulties. It’s Paul frankly owning up to his role [in creating their problems].”

When McCartney sings lyrics such as “I never gave you my pillow,” Womack says, “He’s basically confessing that he could have been a better friend, that he could have provided comfort, but he didn’t.”

“The End”

“When a band tells you they’ve got a song called ‘The End,’ you’ve gotta start wondering if they’re gonna be a band much longer,” Womack says.

Each of the Beatles takes an instrumental solo on the track. “You start off with Ringo’s amazing drum rumble,” says Womack, “which he borrowed from ‘In-A-Gadda-Da-Vida,’ the hit late-1960s [1968] song by Iron Butterfly.

“Her Majesty”

This little ditty, which McCartney wrote about Queen Elizabeth II, almost didn’t make the cut after the Beatles didn’t like its placement in the middle of the medley on Side 2. “One of the engineers cut it out with a razor blade, and the Beatles meant for him to throw it away,” explains Flanagan. “But they had a rule at [Apple Records distributor] EMI: Never throw away anything by the Beatles. So he taped it to the end of the reel. So they’re listening back to the album … and on comes ‘Her Majesty.’ The engineer is embarrassed, and they go, ‘No, actually that’s great!’”