"Stairway to Heaven" continues to top radio lists of the greatest rock songs, including a 2006 "Guitar World" readers poll of greatest guitar solos. On the 20th anniversary of the original release of the song, it was announced via U.S. radio sources that the song had logged up an estimated 2,874,000 radio plays. As of 2000, the song had been broadcast on radio over three million times. In 1990, a St. Petersburg, Florida station kicked off its all-Led Zeppelin format by playing "Stairway to Heaven" for 24 hours straight. It is also the biggest-selling single piece of sheet music in rock history, clocking up an average of 15,000 copies yearly. In total, over one million copies have been sold.