Vietnam Veterans Memorial, Washington
This V-shaped memorial lists the names of the American dead and missing in the Vietnam conflict, which had embroiled the US between 1955 and 1973.
The cost of Vietnam War was huge for the US, as the rising manpower requirements eventually culminated in a mandatory draft, which proved deeply unpopular. Many Vietnam veterans suffered from severe post-traumatic stress disorder, and suffered even more when mental health programs were cut back in the 1980s. And despite the effort the US expended in order to contain the spread of Communism in Southeast Asia, it was in vain, as America's ally South Vietnam was corrupt to the core and lacked legitimacy. The US had to give up and withdraw in 1973, and South Vietnam fell in 1975.
(Of course, South Vietnam, now exiled in Southern California, would beg to disagree - and its own Vietnam War memorial in Westminster, California, carries that different tone.)