American popular music hit a milestone today as Billboard announced that Katy Perry's breakthrough smash hit "I Kissed a Girl" has officially become the 1,000 #1 single in what Billboard refers to as the rock era. According to the magazine, the rock era began in 1955 when "Rock Around the Clock" by Bill Haley and the Comets reached #1 on what was then called the Best Sellers chart. In August 1958 Billboard's Hot 100 was inaugurated with Ricky Nelson's "Poor Little Fool" at the top.

This is also an important week for the Capitol Records label. Last week, Capitol artist Coldplay reached #1 with the single "Viva La Vida." Katy Perry, who ascends this week, is also a Capitol Records artist. This is the first time Capitol has achieved 2 consecutive #1 hits since 1976 when "Silly Love Songs" by Wings followed the Sylvers' "Boogie Fever" into the top slot.

Compare #1's 53 years apart:

• Watch "Rock Around the Clock"
• Watch "I Kissed a Girl"

_{Single cover courtesy Capitol Records}