Migrant Mother 1936 This California farmworker, age 32, had just sold her tent and the tires off her car to buy food for her seven kids. The family was living on scavenged vegetables and wild birds. Working for the federal government, Dorothea Lange took pictures like this one to document how the Depression colluded with the Dust Bowl to ravage lives. Along with the writing of her economist husband, Paul Taylor, Lange’s work helped convince the public and the government of the need to help field hands. Lange later said that this woman, whose name she did not ask, “seemed to know that my pictures might help her, and so she helped me.”

Birmingham 1963 For years, Birmingham, Ala., was considered “the South’s toughest city,” home to a large black population and a dominant class of whites that met in frequent, open hostility. Birmingham in 1963 had become the cause célèbre of the black civil rights movement as nonviolent demonstrators led by Rev. Martin Luther King Jr. repeatedly faced jail, dogs and high-velocity hoses in their tireless quest to topple segregation. This picture of people being pummeled by a liquid battering ram rallied support for the plight of the blacks.

What Charles Dickens did with words for the underage toilers of London, Lewis Hine did with photographs for the youthful laborers in the United States. In 1908 the National Child Labor Committee was already campaigning to put the nation’s two million young workers back in school when the group hired Hine. The Wisconsin native traveled to half the states, capturing images of children working in mines, mills and on the streets. Here he has photographed “breaker boys,” whose job was to separate coal from slate, in South Pittston, Pa. Once again, pictures swayed the public in a way cold statistics had not, and the country enacted laws banning child labor.

Tiananmen Square 1989 A hunger strike by 3,000 students in Beijing had grown to a protest of more than a million as the injustices of a nation cried for reform. For seven weeks the people and the People’s Republic, in the person of soldiers dispatched by a riven Communist Party, warily eyed each other as the world waited. When this young man simply would not move, standing with his meager bags before a line of tanks, a hero was born. A second hero emerged as the tank driver refused to crush the man, and instead drove his killing machine around him. Soon this dream would end, and blood would fill Tiananmen. But this picture had shown a billion Chinese that there is hope.

Shanghai Bombed 1937 Japan launched its bid to annex China in July, 1937, following years of planning. The bombing of Shanghai on August 4, “Bloody Saturday,” was appalling in the price paid by helpless citizens. The photo of this child deserted at the train station jarred its beholders, and with the Massacre of Nanking four months later – a barbaric massacre of more than 300, 000 Chinese – the image of the quiet, tea drinking Japanese was forever altered. This early awareness of Japanese war atrocities helped fuel the subsequent American revulsion at – and response to – the attack on Pearl Harbor.