Queued up on the turntable is what many music experts consider to be the first "Rock & Roll" song, "Rocket 88" by Jackie Brenston from 1951.
Scroll down to follow the evolution of Rock 'n' Roll.

Alan Freed (1921-1965)

Alan Freed is commonly referred to as the "Father of Rock 'n' Roll" due to his promotion of the style of music, and his introduction of the phrase "Rock and Roll", in reference to the musical genre, on mainstream radio in the early 1950s. On July 11, 1951, Freed began playing rhythm and blues records on WJW, Cleveland, Ohio. While R&B records were played for many years on lower powered, inner city radio stations aimed at African-Americans, this is arguably the first time that authentic R&B was featured regularly on a major, mass audience station. Freed called his show "The Moondog House" and billed himself as "The King of the Moondoggers". He had been inspired by an offbeat instrumental called "Moondog Symphony" that had been recorded by New York street musician Louis T. Hardin, aka "Moondog". Freed adopted the record as his show's theme music. His on-air manner was energetic, in contrast to many contemporary radio presenters of traditional pop music, who tended to sound more subdued and low-key in manner. He addressed his listeners as if they were all part of a make-believe kingdom of hipsters, united in their love for black music. He also began popularizing the phrase "Rock and Roll" to describe the music he played.
The two major ingredients involved in the origin and evolution of "Rock and Roll" were the intruduction of the 45 RPM record by RCA in March, 1949 and Alan Freed's pioneering introduction of "Rock and Roll" to main-stream America. Between the years 1949 and 1954, popular AM radio play and the "Top 10 Record Charts" were dominated by mostly white singers and their middle-of-the-road tunes. But on July 17th, 1954 something musically ground-breaking took place. For the very first time, a "Rock and Roll" song made it onto the Billboard Top Ten Chart. It was "Sh-Boom" by the Chords. This was the beginning, and by January, 1957 almost all top 30 Billboard songs were catagoized as "Rock and Roll". In the span of only 30 months the whole popular music landscape changed completely. The graph below illustrates month-by month how this new music made its impact on the popular record charts.

BILLBOARD Top Ten Charts from July, 1954 to December, 1956
(RED indicating the position of a "Rock And Roll" song)
Jul 1954Aug 1954Sep 1954Oct 1954Nov 1954Dec 1954 Jan 1955Feb 1955Mar 1955Apr 1955May 1955Jun 1955 Jul 1955Aug 1955Sep 1955Oct 1955Nov 1955Dec 1955 Jan 1956Feb 1956Mar 1956Apr 1956May 1956Jun 1956 Jul 1956Aug 1956Sep 1956Oct 1956Nov 1956Dec 1956
1111111111 1111111111 1111111111
2222222222 2222222222 2222222222
3333333333 3333333333 3333333333
4444444444 4444444444 4444444444
5555555555 5555555555 5555555555
6666666666 6666666666 6666666666
7 777777777 7777777777 7777777777
8888888888 8888888888 8888888888
9999999999 9999999999 9999999999
10101010101010101010 10101010101010101010 10101010101010101010
History of Songs Incorporating the Words 'Rock' and 'Roll'
       First song to put the words Rock and Roll together, from 1951
Rockin' And Rollin' Tommy Scott
       First Rock and Roll song to hit the Billboard Top Ten, July 17, 1954
Sh-Boom The Chords
       First Number One Rock and Roll song to hit the charts, July 9, 1955
Rock Around The Clock Bill Haley & Comets