APRIL 20

1980:Cuban President Fidel Castro allows Cubans to board boats and flee to Florida. About 125,000 leave in the “Mariel boatlift.”

1971: James Swann, his parents and nine other families win their case as the Supreme Court upholds busing as a way to racially integrate schools.

1999: Two Columbine High School students murder 13 people before killing themselves.