December 1, 1955 – December 1956
Rosa Parks is arrested for refusing to give up her seat to a white passenger, sparking a year-long bus boycott in Montgomery, Alabama.
Results of a mass field trial show Jonas Salk's polio vaccine to be safe and effective, opening the way to mass vaccination.
A conflict between North Vietnam and the Viet Cong on one side and South Vietnam, backed by the United States and its allies, on the other; it ends with the fall of Saigon in 1975.
During the 300-day free-movement period after the Geneva Accords, roughly 800,000 to one million people, many of them Catholics, move from North to South Vietnam.
The US Supreme Court rules that racial segregation in public schools is unconstitutional.
Japan signs a peace treaty with the Allied powers, ending the occupation when it takes effect in 1952.
North Korean forces cross the 38th parallel; the war, drawing in US-led UN forces and China, ends in an armistice in 1953.