To see what the current state of classic rock in the United States looks like, I monitored 25 classic rock radio stations1 operating in 30 of the country’s largest metropolitan areas for a week in June.2 The result, after some substantial data cleaning, was a list of 2,230 unique songs by 475 unique artists, with a total record of 37,665 coded song plays across the stations.

I found that classic rock is more than just music from a certain era, and that it changes depending on where you live. What plays in New York — a disproportionate amount of Billy Joel, for example — won’t necessarily fly in San Antonio, which prefers Mötley Crüe. Classic rock is heavily influenced by region, and in ways that are unexpected. For example, Los Angeles is playing Pearl Jam, a band most popular in the 1990s, five times more frequently than the rest of the country. Boston is playing the ’70s-era Allman Brothers six times more frequently.

To put today’s classic rock on a timeline, I pulled the listed release years for songs in the set from the music database SongFacts.com. While I wasn’t able to get complete coverage, I was able to get an accurate release year for 74 percent of the 2,230 songs and 89 percent of the 37,665 song plays.3 The earliest songs in our set date back to the early 1960s;4 the vast majority of those are Beatles songs, with a few exceptions from The Kinks and one from Booker T. and the MGs. A large number of songs appeared from the mid-’60s through the early ’70s. Classic rock peaked — by song plays — in 1973. In fairness, that was a huge year — with the release of Pink Floyd’s “Dark Side of the Moon”(an album of classic rock staples), Led Zeppelin’s “Houses of the Holy” and Elton John’s “Goodbye Yellow Brick Road”5 — but the trend steadily held for the rest of the ’70s and through the mid-’80s.