What year marked the beginning of American involvement in Vietnam?

The year that marked the beginning of significant American involvement in Vietnam is 1954. This period is recognized as the start of U.S. military and political engagement in Vietnam, particularly as the country was transitioning from French colonial rule to the conflict between North and South Vietnam. The U.S. began to provide military assistance and advisory support to the South Vietnamese government, following the Geneva Accords which divided Vietnam.

American involvement intensified in the following years, particularly after the Gulf of Tonkin incident in 1964, which led to a dramatic escalation of U.S. military presence. Therefore, while 1960 and later years saw an increase in American involvement, it was 1954 when the groundwork for U.S. engagement was laid down, making it the correct answer to the question regarding the beginning of American involvement in Vietnam.