If you happened to be driving through a busy intersection in a major American city this September, you might have seen a cryptic message from Drake. Leading up to the release of Certified Lover Boy, dozens of billboards began popping up around the country, dropping hints about who would be featured on the album.

“Hey Toronto, the best rapper alive signed me in 2009 and is on CLB,” one message read, referring to Young Money’s Lil Wayne. Another billboard near New York City’s Times Square read: “Hey New York, the GOAT is on CLB.”

Just in the past few months, we’ve seen billboard campaigns from artists like Drake, Kanye, Lil Nas X, and Key Glock go viral online. Artists and labels have been using billboard marketing for decades, but the tactic has evolved over time. Now, in the social media era, billboards can reach a lot more people than just those who happen to be in the same physical location as the sign. If executed correctly, photos and videos of the billboards can spread quickly online, going viral and reaching millions of people across the world.

To understand the evolution of billboard marketing in music, you have to go back to the beginning. Jac Holzman, founder of Elektra Records, is credited as one of the first to popularize the advertising method in music. After The Doors finished their debut self-titled album in 1966, Elektra Records was looking for ways to put the emerging group on the map. After some brainstorming, Holzman picked a location near the Chateau Marmont hotel on Sunset Boulevard in Los Angeles and inquired with an ad company about a billboard to advertise the new band. Just like that, for $1,200 a month, Holzman reserved a billboard for the entire year. 

“I wanted artists and DJs and writers to know that we were here,” Holzman tells Complex. “If you are a DJ or if you are a program manager, you get tons and tons of stuff on your desk every day, and it’s going to get lost. I thought this would call their attention, because they can’t help but see it. They’ve got to see it as they drive to or from work. Because they’re in a car, they’re paying singular attention, and we had an opportunity, if only a few seconds, to let them see and absorb it.” 

The Doors’ billboard was an instant success. Holzman says he received calls from “several record salesmen” who were intrigued by the band, and many inquisitive bystanders went out and played the band’s music. Other labels took note, too, and billboards soon became an important part of any album rollout.

The same method that Holzman used for The Doors’ first billboard is still alive today, but it’s gone through some changes in the digital age. The rise of online marketing once threatened to render physical advertising obsolete, but some forward-thinking companies have figured out how to make billboards even more impactful in the social media era.