On March 31, 1870 Thomas Mundy Peterson, the son of slaves, did something that no African-American had ever done before: he voted.

Slavery had been formally abolished five years earlier, and the 15th Amendment to the US Constitution had established that “the right of citizens of the United States to vote shall not be denied or abridged by any state on account of race, colour or previous condition of servitude”.

Tom Peterson, a 47-year-old school janitor, exercised that right in Amboy, New Jersey, casting his vote under the angry stares of the town’s white inhabitants. He voted Republican, in recognition of Abraham Lincoln, the Great Emancipator.

Peterson’s humble and courageous act reaches forward to the election of Barack Obama, and back through the generations of black people taken from Africa and forced to live in American servitude. The idea that a black man could vote would have been as unimaginable to Peterson’s slave ancestors as the idea of a black president would have been unthinkable to Peterson himself.

Times Archive, 1963: Let freedom ring

'All this will end one day. We will hew hope out of the mountain of despair'

• Topic: The assassination of Martin Luther King

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We imagine history to happen in a linear progression, in this instance a straight line from bondage to freedom to civil rights to equal rights, from Mundy to Martin Luther King to Barack Obama. But history — least of all the tortured history of black America — does not work that way.

For a brief period after emancipation, black democracy seemed about to flourish. Two black men, one a preacher, Hiram Revels, and the other a teacher, Blanche Bruse, were elected to the US Senate from Mississippi. To this day they are the only African-Americans ever to represent a Southern state in the Senate.

The dream of black democracy swiftly evaporated. The Ku Klux Klan had aleady come into being at the end of the Civil War in 1865. As Reconstruction collapsed after a few years, black voting rights were suppressed, racial segregation was imposed, lynchings, race riots and school burnings spread.

State-sanctioned racism emerged in the Southern states but infected the North. The systematic oppression of one race by the other in the “Jim Crow” system of laws would remain virtually intact until the 1950s. In Southern states blacks could not vote or sit on juries or take part in enforcing the law. Blacks could not go to the same schools as white people; they could not eat in the same restaurants, travel on the same train cars, live in the same neighbourhoods, or shop in the same places.

Between 1889 and 1922 about 3,500 people were lynched, most of them black men. This form of murder cruelly emphasised the powerlessness of the victim: the killing took place in public, the guilty were known to all, and effectively immune from prosecution.

From about 1915 black Americans headed north and west in huge numbers to escape the persecution, in what became know as the Great Migration. Slowly, painfully, African-Americans fought back, through litigation, education and lobbying. Campaigns of civil disobedience and direct action evolved into the civil rights movement.

In 1954 the Supreme Court finally outlawed segregation in schools. A year later a young seamstress named Rosa Parks refused to give up her seat to a white person on an Alabama bus. She was, she said, “tired of giving in”. She was arrested, sparking the Montgomery bus boycott and huge protests.

Six-year-old Ruby Bridges was accompanied to school by federal marshals in 1960, to become the first African-American pupil at the all-white William Franz School in New Orleans. The white pupils at the school promptly left, and all but one teacher. For more than a year, Ruby Bridges was taught alone.

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