Girl Groups. Beatles. Beach Boys. Elvis.

Released in October 1959, Marty Robbins' Grammy Award-winning "El Paso" was the first No. 1 of the 1960s. Accompanied by Spanish guitar, the haunting song (later covered by the Grateful Dead) was one of four country records-along with Bobbie Gentry's "Ode to Billy Joe," Bobby Goldsboro's "Honey" and Jeannie C. Riley's "Harper Valley P.T.A."-to hit the No. 1 pop slot during the decade.

The early '60s produced singers like Steve Lawrence, Connie Francis and Bobby Vinton, who all sang No. 1 songs that appealed to parents as much as they did to their children. Instrumentals-the kind parents liked-were also big. Seven such numbers hit the top, including Paul Mariat's "Love Is Blue" and Lawrence Welk's "Calcutta," which bumped the Shirelles' "Will You Still Love Me Tomorrow." It was the only No. 1 single of Welk's long career.

The decade's first four years sweetened up the "dangerous" rock'n'roll sound that originated in the mid-'50s. Songs like the Drifters' "Save the Last Dance for Me," Dion's "Runaround Sue," Gene Chandler's "Duke of Earl" and Gary "U.S." Bonds' "Three O'Clock" would've been at home atop the chart during the latter half of the '50s. So would dance-craze songs from Chubby Checker and Joey Dee & the Starlighters and novelties like Bobby "Boris" Pickett's "Monster Mash." And it's difficult to believe that time has forgotten Larry Verne's "Mr. Custer," a masterpiece about a coward who wanted no part of the titular character's last stand.

Let's not forget the girl groups who delivered a dozen No. 1s during the '60s with the help of Brill Building writers, including the Angels' "My Boyfriend's Back" (by Bob Feldman, Jerry Goldstein and Richard Gottehrer), the Crystals' "He's a Rebel" (Gene Pitney and Phil Spector), the Dixie Cups' "Chapel of Love" (Spector, Jeff Barry and Ellie Greenwich) and the Shangri- Las' "Leader of the Pack" (Barry, Greenwich and Shadow Morton).

The '60s had plenty of No. 1s by giants whose music would defy the constraints of time: Elvis Presley, with six chart-toppers; Roy Orbison, with two; and Ray Charles, three. Presley's first No. 1 of the '60s, "Stuck on You," scored the top spot on Aug. 15, 1960. Not only was it his first hit after a two-year stint in the U.S. Army, it was also the first of five No. 1s, all with the Jordanaires, that he would have during the next two years. But after "Good Luck Charm" peaked at No. 1 on April 21, 1962, Presley wouldn't return to the summit until Nov. 1, 1969, with "Suspicious Minds."

Charles' first No. 1 of the decade was "Georgia on My Mind." It lasted there one week, while his next, "Hit the Road Jack," had a two-week stint beginning Oct. 9, 1961. The next year, Charles snared his longest stay in the penthouse with "I Can't Stop Loving You," which ruled from June 2 until it was displaced by "The Stripper," from David Rose & His Orchestra, on July 7.

Orbison's "Running Scared" had a two-week stay at the top in June 1961, while "Pretty Woman" lasted three weeks, beginning Sept. 26, 1964.

If the '50s laid the foundation for rock and R&B, the '60s gave those genres blueprints for the future. Practically every other sound and subgenre that would emerge during the next five decades can trace its origins back to the '60s-quite an accomplishment considering the music industry is always waiting for the next big thing to break through. And that big of a thing has occurred, genre-wise, only about four times in the last 40 years: disco, rap, punk and heavy metal.

Most of those genres would, one way or another, begin with the Beatles, who had 18 No. 1s. The Fab Four redefined pop culture during their seven-year ride at the top of Billboard's charts. From the first chord of "I Want to Hold Your Hand," which hit the top on Jan. 18, 1964, to the band's last No. 1, "Come Together," on Oct. 18, 1969, the Beatles changed everything, from the way Americans wore their hair and dressed to how they started listening to music, including looking for hidden meanings in lyrics. And on the Beatles' coattails were another 19 No. 1s from Brit bands like the Rolling Stones, the Dave Clark Five, Herman's Hermits and the Animals.

And American acts responded in turn, with nearly 30 No. 1 hits. Some of the bands aspired to sound like the Beatles, including the Turtles ("Happy Together" reigned for three weeks in 1967), who took their name because it ended with the same letters. And along with Simon & Garfunkel, the Doors and the Young Rascals, there were the Beach Boys, whose surf sound hit the top 10 prior to the Beatles. The band's last No. 1 of the decade was "Good Vibrations" in 1966, but the Beach Boys and Beatles spent most of the rest of the decade trying to outdo each other.

Coinciding with the British Invasion was Motown, which practically created its own genre, landing 18 songs atop the Hot 100, including 12 from the Supremes. And the old guard-Frank Sinatra and Dean Martin-also managed to land No. 1s on the chart.

The '60s were the decade when many artists took control, writing their own songs and in some instances designing their own album covers. It is, in fact, the only time in music history when the most popular sounds were also consistently the most creative, experimental and critically acclaimed music. That may be due to the fact that when the '60s began, the single was still the main artistic configuration, despite the album's commercial introduction in 1948, Sinatra's attempt to establish the long-form as an artistic statement in the mid-'50s and its ability to generate more revenue than the single, thanks to its higher price.

By the decade's end, the album would establish itself as the dominant form, a notion that's only now being challenged some 50 years later. But during the '60s, the single was the main vehicle for many an artistic triumph.