On May 4, 1493, Pope Alexander VI promulgated the Line of Demarcation, dividing the New World between Spain and Portugal in response the return of Christopher Columbus from his discovery of the American continents. However, neither country was entirely satisfied with the placement of the Line. A year later on June 7, 1494, the two nations signed the Treaty of Tordesillas, which moved the Line of Demarcation further west, giving Portugal claim to Brazil.

On May 4, 1970, National Guardsmen at Kent State University opened fire on students protesting the US invasion of Cambodia, killing four.

Review a legal chronology of the Kent State shootings, from May 5, 1970 (the day the FBI investigation started) to January 4, 1979 (the day the state of Ohio reached an out-of-court settlement for $675,000 with victims and relatives of victims).