"Black Water" emerged as the Doobie Brothers' first-ever No. 1 song when a savvy Virginia disc jockey discovered it after he flipped over one of their singles. WROV-AM was situated near a tributary of the Roanoke River called the Blackwater, and listeners quickly made the song a local anthem.

But that was hardly the first – or last – time something like this has occurred. In fact, rock history is dotted with examples of B-sides that became big hits. We're focusing on songs that charted separately, rather than examples like the Beatles' "Something" / "Come Together" single, when sales were combined.

Sometimes, this A or B decision has been made purposefully: The Rolling Stones and Beach Boys, for instance, also issued so-called "double-A" sides that were meant to showcase two worthy songs. Other times, mistakes were simply made: A band, or their record label, wasn't able to correctly gauge what might hit home with the larger listening audience.

And, quite frankly, occasionally things just happen. As with the Doobie Brothers, a connection is made that simply couldn't have been predicted: That's how you end up with a smash like "Beth," even though this ballad had so little in common with Kiss' other work.

It hasn't always gone smoothly. In fact, a disagreement over B-side placement for "I Am the Walrus" created some of the first notable fissures on the way to the Beatles' split. "I got sick and tired of being [bandmate] Paul [McCartney]'s backup band," John Lennon later admitted.

Fleetwood Mac ended up returning to an unjustly overlooked B-side decades later. Then there were the tracks that kept getting released until somebody finally noticed them. How ever they got there, each song on the following list has one thing in common: They're all B-sides that became big hits.

20 B-Sides That Became Big Hits

We're focusing on songs that charted separately, rather than so-called "double A-sides."

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