MOMENTS IN TIME

• On April 9, 1939, black contralto Marian Anderson gives a free open-air concert at the Lincoln Memorial. She had been scheduled to sing at Washington's Constitution Hall, but the Daughters of the American Revolution denied her the right to perform because of her race.

• On April 10, 1963, the USS Thresher, an atomic submarine, sinks in the Atlantic Ocean, killing its entire crew. One hundred and twenty-nine sailors and civilians were lost when the sub unexpectedly plunged to the sea floor 300 miles off the coast of New England.

• On April 11, 1917, composer Scott Joplin, the "King of Ragtime," dies in New York City. His "Maple Leaf Rag" of 1899 launched a national craze for ragtime music, and he composed many other popular ragtime songs, including "The Entertainer."

• On April 12, 1954, Bill Haley and his band, the Comets, record "Rock Around the Clock." Two years later the song became a hit when it was used as a theme for the movie "Blackboard Jungle," becoming the first rock 'n' roll song to reach No. 1.

• On April 13, 1970, disaster strikes 200,000 miles from Earth when oxygen tank No. 2 blows up on Apollo 13, the third manned lunar landing mission. Mission commander Lovell reported to mission control on Earth: "Houston, we've had a problem here."

• On April 14, 1912, just before midnight in the North Atlantic, the RMS Titanic hits an iceberg, rupturing five watertight compartments along her starboard side. Hours later the massive vessel sank, and more than 1,500 people died in the icy North Atlantic waters.

• On April 15, 1927, Douglas Fairbanks, Mary Pickford and Norma and Constance Talmadge become the first celebrities to leave their footprints in cement at Grauman's Chinese Theater. The future Hollywood landmark was still under construction at the time.