1948 – LP's

In 1948 Columbia introduced the Long Playing "microgroove" LP record format (sometimes written "Lp" in early advertisements), which rotated at 33⅓ revolutions per minute, to be the standard for the gramophone record for half a century.

The 33's eventually caused one of the first real wars between similar formats of records. When the LP was introduced in 1948, the 78 was the conventional format for phonograph records. By 1952, 78s accounted for slightly more than half of the units sold in the United States, and just under half of the dollar sales. The 45, oriented toward the single song, accounted for 30.2% of unit sales and 26.5% of dollar sales. The LP represented 16.7% of unit sales and 26.2% of dollar sales.

"78 Speed On Way Out; LP-45 Trend Gaining", The Billboard, August 2, 1952, p. 47.

Ten years after their introduction, the share of unit sales for LPs in the U.S. was 24.4%, and of dollar sales 58%. Most of the remainder was taken up by the 45; 78s accounted for only 2.1% of unit sales and 1.2% of dollar sales.

Robert Shelton (March 16, 1958). "Happy Tunes on Cash Registers". The New York Times. p. XX14.

It took almost 10 years to set LP as a standard for music industry, but by 1954 RIIA and recording companies agreed to accept LP's as the most common format for a record, and in 1963 it was officially announced in RIIA bulletins.

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