60 years ago: first LP

Columbia Records unveiled the LP at a press conference in the Waldorf Astoria on June 21, 1948, the summer solstice and thus the longest day of the year, in two formats: 10in (25cm) in diameter, matching that of 78rpm singles, and 12in (30cm) in diameter.

Although they released approximately 50 simultaneously to allow for a purchasing catalogue, the first catalogue number for a ten-inch LP, CL 6001, was a reissue of the Frank Sinatra 78 rpm album set The Voice of Frank Sinatra; the first catalogue number for a twelve-inch LP, ML 4001, was the Beethoven Violin Concerto in D played by Nathan Milstein with the New York Philharmonic conducted by Bruno Walter. These two albums are therefore the first long-players.

see wiki