"The End" is a song (music by Jimmy Krondes and lyrics by Sid Jacobson) which was released (in the United States) as a 1958 single by Earl Grant. Grant's single on the Decca label, featured Charles "Bud" Dant on orchestra; some pressings of the single were shown with the title "(At) The End (Of A Rainbow)". The single was Grant's only entry into the U.S. Top 40, and spent 19 weeks on the Billboard Hot 100 reaching No. 7, while reaching No. 16 on Billboard's "Hot R&B Sides".

Who sang at the end of the rainbow? Let's have some stream of consciousness first.
The relevant information to answer the above question is: "The End" is a song (music by Jimmy Krondes and lyrics by Sid Jacobson) which was released (in the United States) as a 1958 single by Earl Grant. So, the answer is Earl Grant.