Her six novels, including Song of Solomon, Beloved and Jazz, express her social and moral judgement, and the Academy said she was a 'literary artist of the first rank' who 'gives life to an essential aspect of American reality'.
Elsewhere the 62-year-old Morrison has been praised for her ability to 'reimagine the lost history of her people, their love and their nightmare passage and redemptive music'.
For others, Morrison was not a deserving artist but merely the lucky beneficiary of social and cultural goodwill. 'I hope the prize inspires her to write better books,' said Stanley Crouch. 'She has a certain skill, but no serious artistic integrity.' One of her fiercest critics, Mr Crouch once blasted her novel Beloved, about slaves and ex-slaves during the Civil War era. 'It seems to have been written in order to enter American slavery into the big-time martyr ratings contest,' he wrote in New Republic. 'We learn little about the souls of human beings, we are only told what will happen if they are treated very badly. The world exists in a purple haze of overstatement, of false voices, of strained homilies; nothing very subtle is ever tried.'
But whatever the judgement about her worthiness for last week's award, the fact of her winning emphasises that this is an extraordinary time for black women writers in America. Rita Dove is the current poet laureate, Maya Angelou was chosen by President Clinton as the poet for his January inauguration. Even Morrison's critics admit her key role in helping to nurture contemporary black women writers, whose works have generated a loyal following and are read more widely across the racial divide than those of their black male counterparts.
The discovery of this lost collective voice is an important moment in American literature, and the Swedish Academy clearly wanted to recognise it. Morrison herself said the prize 'feels expanded somehow, like a very large honour, because one can share it with more people than one's neighbourhood or one's family. I feel like it's shared among us.'
Perhaps she was referring not only to her contemporaries but also to the muffled voices of the years of slavery, when black people were forbidden to read and write. Some slave writers not only had to escape their masters; they were also forced to flee the country. Even after the abolition of slavery, many black authors were forced to distribute their accounts of lynchings, segregation and discrimination among friends and church members.
Those writers who were befriended by sympathetic white Americans often had to moderate their texts and tone down their views of racism in order to be published. Several recent university projects have concentrated on these early, neglected works, following a dusty trail through attics, basements and libraries.
One of the first novels by a black American woman, published in America in 1859, was lost for years until researchers from Yale University republished it in 1983. It was called Our Nig, or Sketches from the Life of a Free Black, by Harriet Wilson. Parts of the author's life mirrored that of the heroine, who was an indentured servant to a brutal white family in 19th-century Massachusetts. One explanation offered by researchers for its suppression is its account of an inter-racial marriage.
The Harlem renaissance from 1919-40 saw the publication of the acknowledged bible of black women's literature, Their Eyes were Watching God, by Zora Neale Hurston. In 1938, Hurston reminded readers that 'only three generations separate the Negro from the muteness of slavery'. Her obligation, as she saw it, was to write about the black Americans' struggle lest one 'be considered forgetful of our past and present'.
The 1960s were dominated by strongly political books, mostly by black men - Stokely Carmichael, Leroi Jones, Eldridge Cleaver and H Rap Brown - addressing, and accusing white people about, the plight of the black underclass.
In the 1970s, the talk was less of black power and a divided nation and more of women's liberation. Toni Morrison, Toni Cade Bambara, Alice Walker, Gayl Jones and others all set out to fill the historical gap, and what Morrison has called 'huge silences in literature' about black women in slavery. Another aim was to dismantle the popular concept that black people handed down only oral history.
Henry Louis Gates, chairman of the Afro-American studies department at Harvard University, casts these writers in a battle against the twin scourges of sexism and racism.
A Portuguese seaman turned plantation owner, he took her out of the field when she was still a child and put her to work in his whorehouse . . . she was the pretty little one with the almond eyes and coffee-bean skin, his favourite.
Gayl Jones from Corrigedora Morrison had heard of such things. A sharecropper's daughter, she was born in 1931 in Lorain, Ohio, a small steel town. When her father fell behind with the dollars 4-a-month rent, the landlord set fire to the house while the family was in it. Her novels contain equally unpleasant and brutal scenes.
Her first two - The Bluest Eye, about a little black girl who thinks everything would be all right if only she had blue eyes, and Sula, the story of an evil woman who inspires goodness - received good notices. Her 1977 Song of Solomon put her on the cover of Newsweek. Beloved, which won the Pulitzer Prize in 1988, is about a fleeing slave who hears her pursuers closing in, and cuts the throat of her two- year-old daughter rather than have her return to servitude.
When the four horsemen came - schoolteacher, one nephew, one slave catcher and a sheriff - the house on Bluestone Road was so quiet they thought they were too late. Three of them dismounted, one stayed in the saddle, his rifle ready, his eyes trained away from the house to the left and to the right, because likely as not the fugitive would make a dash for it. Although sometimes you could never tell, you'd find them folded up tight somewhere: beneath floorboards, in a pantry - once in a chimney . . . and when you reached for the rope to tie him, well, even then you couldn't tell. The very nigger with his head hanging and a little jelly-jar smile on his face could all of a sudden roar, like a bull or some such, and commence to do disbelievable things.