Louis (Louis, Hebrew name Aryeh-Leib) Bernstein was born on 25 August 1918 in Lawrence, Massachusetts, to a Jewish family who came from Rivne (Ukraine): mother Jenny (née Reznik), father Samuel Joseph Bernstein, a wholesale hairdresser (according to some sources, owned a bookstore). His grandmother insisted that the child be named Louis, but his parents always called him Leonard. He officially changed his name to Leonard at the age of fifteen, shortly after his grandmother died. To his friends and many others, he was simply "Lenny." His father did not encourage young Leonard's interest in music at first, although he did take the boy to concerts and eventually supported his musical education. In his youth, Bernstein intended to become a pianist, and began taking piano lessons as a child, attending Garrison and Boston Latin schools. He studied composition at Harvard University with Walter Piston, Edward Burlingame-Hill and A. Tillman Merritt. Even before graduating in 1939, Bernstein made his unofficial debut as a conductor with his own music for The Birds, and played and conducted in Marc Blitzstein's The Cradle Will Rock. Later he studied at the Curtis Institute of Music with Fritz Reiner (conducting), Randall Thompson (orchestration), Richard Stöhr (counterpoint) and Isabella Vengerova (piano). In 1940 Bernstein attended summer school at the Boston Symphony Orchestra (Tanglewood Music Centre) under Sergei Koussevitzky and later became his assistant.
He was assistant conductor (1943-1944), conductor (1957-1958), and principal conductor (1958-1969) of the New York Philharmonic (where he succeeded Bruno Walter) and the New York City Symphony (1945-1948).
In 1953 Bernstein became the first American conductor at La Scala, collaborating with Maria Callas. On 22 August 1959, the Grand Hall of the Moscow Conservatory hosted the opening of the New York Orchestra's concert tour under Leonard Bernstein. This tour included seventeen countries (three weeks in the USSR) and fifty concerts. The final concert was performed at the White House, Washington, D.C. Winner of the Siemens Prize (1987). Author of The Joy of Music (1959) and The Infinite Variety of Music (1966), Young People's Concerts, The Unanswered Question (1976), Findings (1982), inducted into the National Songwriters Hall of Fame in 1971, Bernstein was forced to cancel several performances in the United States and Japan in early 1990 for health reasons. He last conducted on 19 August in Tanglewood, Massachusetts, when the Boston Symphony Orchestra performed B. Britten's Four Sea Interludes and Beethoven's Seventh Symphony. During the performance of the third movement of the symphony, the conductor began coughing fits (he could not get rid of his smoking habit). He died of a heart attack on 14 October 1990. He is buried at Green-Wood Cemetery in New York.