I'm thinking that it was known as breaking the racial barrier when Jackie Robinson first played for the Brooklyn Dodgers.
Jackie Robinson's greatest MLB accomplishment was breaking the color line, when he debuted for the Brooklyn Dodgers in 1947.
In 1947, Robinson broke the major leagues' color barrier when he debuted with the Dodgers.
No one broke the color barrier in 1946, however in 1947 Jackie Robinson broke it by playing for the Brooklyn Dodgers.
Bill Antonello debuted on April 30, 1953, playing for the Brooklyn Dodgers at Ebbets Field; he played his final game on September 27, 1953, playing for the Brooklyn Dodgers at Ebbets Field.
Dan Bankhead debuted on August 26, 1947, playing for the Brooklyn Dodgers at Ebbets Field; he played his final game on July 18, 1951, playing for the Brooklyn Dodgers at Ebbets Field.
Rex Barney debuted on August 18, 1943, playing for the Brooklyn Dodgers at Ebbets Field; he played his final game on September 4, 1950, playing for the Brooklyn Dodgers at Ebbets Field.
Boyd Bartley debuted on May 30, 1943, playing for the Brooklyn Dodgers at Ebbets Field; he played his final game on June 7, 1943, playing for the Brooklyn Dodgers at Ebbets Field.
Ralph Branca debuted on June 12, 1944, playing for the Brooklyn Dodgers at Ebbets Field; he played his final game on September 7, 1956, playing for the Brooklyn Dodgers at Ebbets Field.
Lindsay Brown debuted on July 13, 1937, playing for the Brooklyn Dodgers at Ebbets Field; he played his final game on October 3, 1937, playing for the Brooklyn Dodgers at Ebbets Field.
Cy Buker debuted on May 17, 1945, playing for the Brooklyn Dodgers at Ebbets Field; he played his final game on September 23, 1945, playing for the Brooklyn Dodgers at Ebbets Field.
Al Campanis debuted on September 23, 1943, playing for the Brooklyn Dodgers at Ebbets Field; he played his final game on October 3, 1943, playing for the Brooklyn Dodgers at Ebbets Field.