What year did 45 rpm records come out?
The 7-inch 45 rpm record was released 31 March 1949 by RCA Victor as a smaller, more durable and higher-fidelity replacement for the 78 rpm shellac discs. The first 45 rpm records were monaural, with recordings on both sides of the disc. As stereo recordings became popular in the 1960s, almost all 45 rpm records were produced in stereo by the early 1970s. Columbia Records, which had released the  rpm 12-inch vinyl LP in June 1948, also released  rpm 7-inch vinyl singles in March 1949, but they were soon eclipsed by the RCA Victor 45. The first regular production 45 rpm record pressed was "PeeWee the Piccolo" RCA Victor 47-0146 pressed 7 December 1948 at the Sherman Avenue plant in Indianapolis, R.O. Price, plant manager.
What year did 7-inch 45 rpm records come out?
31 March 1949
Single (music)
The 7-inch 45 rpm record was released 31 March 1949 by RCA Victor as a smaller, more durable and higher-fidelity replacement for the 78 rpm shellac discs. The first 45 rpm records were monaural, with recordings on both sides of the disc. As stereo recordings became popular in the 1960s, almost all 45 rpm records were produced in stereo by the early 1970s. Columbia Records, which had released the  rpm 12-inch vinyl LP in June 1948, also released  rpm 7-inch vinyl singles in March 1949, but they were soon eclipsed by the RCA Victor 45. The first regular production 45 rpm record pressed was "PeeWee the Piccolo" RCA Victor 47-0146 pressed 7 December 1948 at the Sherman Avenue plant in Indianapolis, R.O. Price, plant manager.
What year were 12-inch 45 rpm records introduced?
1970s
Single (music)
45 RPM
https://en.wikipedia.org/wiki/45%20RPM
Single (music)
https://en.wikipedia.org/wiki/Single%20%28music%29
There are various sizes for 45 rpm records, including 7-inch and 12-inch, which were first released in different years. The 7-inch 45 rpm record came out on 31 March 1949, released by RCA Victor as a smaller, more durable, and higher-fidelity replacement for the 78 rpm shellac discs, while 12-inch 45 rpm records were introduced in the 1970s.