"Top of the World" was released on September 19, 1973 and reached #1 on the Billboard chart on October 6.  This was their 2nd single to reach #1.  It stayed at #1 for two weeks.  Just behind this song at #2 was "Photograph" by Ringo Starr and the second week #2 was "Goodbye Yellow Brick Road" by Elton John.  

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Interesting that this single, although released after "Yesterday Once More", was from the previous album, A Song for You.  The song had been released in Japan and did well.  Lynn Anderson had released a version of the song in the US and it was very successful on the country charts. Richard then decided to release a US single.  He added more instruments to the song and had Karen re-record the lead vocal.