As is widely known, Toni Morrison based Beloved on the story of Margaret Garner, a woman whose trial for infanticide was discussed in the newspapers in 1856. Morrison included a clipping from one newspaper account in a book she was involved in publishing in 1974, The Black Book. (That clipping is included below.) 

What is known about Margaret Garner and Robert Garner's lives is somewhat limited and fragmentary. Still, even with this fragmentary knowledge, it's important to note that there are a number of ways the real Margaret Garner’s story diverges from Morrison’s account in Beloved. The fact that there are differences may not be very important; Beloved is a work of fiction, and Morrison as a novelist has license to reimagine real-life events and individuals to shape the story she wants to tell. That said, the particular nature of the differences is notable and often telling. Far and away, the most significant variation from the historical narrative of Margaret Garner might be the way the story ends: Sethe and Denver are alive and free at the end of Morrison's novel, whereas Margaret Garner was recaptured and died in captivity. 

Below is a screen capture of the newspaper article from 1856 that Morrison read in 1974, which supplied the kernel of the idea. The version Morrison likely saw was published in the National Anti-Slavery Standard, March 15, 1856, though as you can see, that is a reprinting of another version that appeared in The American Baptist on February 12, 1856. 

(Admittedly the image quality is poor; immediately below I have also retyped the text of most of the article for ease of reading):

The author is of this news article is P.S. Barrett, and he chronicles meeting both Margaret Garner and her mother-in-law, who strongly resembles the Baby Suggs we see in the novel. He was able to interview Margaret Garner just about two weeks after the event.

Here are some sections I retyped from the article pasted above: 

From the American Baptist

A VISIT TO THE SLAVE MOTHER WHO KILLED HER CHILD. 

Last Sabbath, after preaching in the city prison, Cincinnati, through the kindness of the Deputy Sheriff, I was permitted to visit the apartment of that unfortunate woman, concerning whom there has been much excitement during the last two weeks. 

 

I found her with an infant in her arms only a few months old, and observed that it had a large [bunch] on its forehead. I inquired the cause of the injury. She then proceeded to give a detailed account of her attempt to kill her children. 

 

She said, that when the officers and slave-holders came to the house in which they were concealed, she caught a shovel and struck two of her children on the head, and then took a knife and cut the throat of the third, and tried to kill the other,--that if they had given her time, she would have killed them all-that with regard to herself, she cared but little; but she was unwilling to have her children suffer as she had done.

 

I inquired if she was not excited almost to madness when she committed the act. No, she replied, I was as cool as I now am; and would much rather kill them at once, and thus end their sufferings, than have them taken back to slavery, and be murdered by piece-meal. 

[...] The two men and the two other children were in another apartment, but her mother-in-law was in the same room. She says she is the mother of eight children, most of whom have been separated from her; that her husband was once separated from her twenty-five years, during which time she did not see him; that could she have prevented it, she would never have permitted him to return, as she did not wish him to witness her sufferings, or be exposed to the brutal treatment he would receive. 

She states that she has been a faithful servant, and in her old age she would not have attempted to obtain her liberty; but as she became feeble, and less capable of performing labor, her master became more and more exacting and brutal in his treatment, until she could stand it no longer; that the effort could result only in death, at most--she therefore made the attempt. 

She witnessed the killing of the child, but said she neither encouraged nor discouraged her daughter-in-law,--for under similar circumstances she should probably have done the same. The old woman is from sixty to seventy years of age, has been a professor of religion about twenty years, and speaks with much feeling of the time she shall be delivered from the power of the oppressor, and dwell with the Savior, ‘where the wicked cease from troubling, and the weary are at rest.’

 

P.S. Bassett

Fairmount Theological Seminary.

Cincinnati (Ohio) Feb. 12, 1856

One immediate similarity between the novel and the historical event presents itself -- a slippage with regard to names and naming. The Gaines family knew Margaret Garner as “Peggy,” but Margaret clearly refused that name in favor of "Margaret Garner." (Her last name came from her husband, Robert Garner, an enslaved Black man.) This slippage reminds one of the way Baby Suggs in the novel is known to the Garners in the novel as “Jenny Whitlow,” a name she has no interest in claiming. She has no “proper” first name; people refer to her as Baby, so that’s the name she identifies with. (There's more on naming and misnaming in Morrison's fiction in our biographical note on Toni Morrison here.) 

One might also note the prominence of the mother-in-law in the story, and the close similarities to Baby Suggs in the novel, including the eight children, most of whom have gone, and the struggles she experienced to perform forced labor as she got older. (Note that here her son didn’t buy her out of slavery with extra labor -- she escaped as part of the Train that also included her son and daughter-in-law and their children.)

Perhaps no case that came under my notice, while engaged in aiding fugitive slaves, attracted more attention and aroused deeper interest and sympathy than the case of Margaret Garner, the slave mother who killed her child rather than see it taken back to slavery. This happened in the latter part of January, 1856. The Ohio River was frozen over at the time, and the opportunity thus offered for escaping to a free State was embraced by a number of slaves living in Kentucky, several miles back from the river. A party of seventeen, belonging to different masters in the same neighborhood, made arrangements to escape together. There was snow on the ground and the roads were smooth, so the plan of going to the river on a sled naturally suggested itself. The time fixed for their flight was Sabbath night, and having managed to get a large sled and two good horses, belonging to one of their masters, the party of seventeen crowded into the sled and started on their hazardous journey in the latter part of the night. They drove the horses at full speed, and at daylight reached the River below Covington, opposite Wester Row. They left the sled and horses here, and as quickly as possible crossed the river on foot. It was now broad daylight, and people were beginning to pass about the streets and the fugitives divided their company that they might not attract so much notice.

An old slave named Simon and his wife Mary, together with their son Robert and his wife Margaret Garner and four children, made their way to the house of a colored man named Kite, who had formerly lived in their neighborhood and had been purchased from slavery by his father, Joe Kite. They had to make several inquiries in order to find Kite's house, which was below Mill Creek, in the lower part of the city. This afterward led to their discovery; they had been seen by a number of persons on their way to Kite's, and were easily traced by pursuers. The other nine fugitives were more fortunate. They made their way up town and found friends who conducted them to safe hiding- places, where they remained until night. They were put on the Underground Railroad, and went safely through to Canada....

In a few minutes...[Kite's] house was surrounded by pursuers -- the masters of the fugitives, with officers and a posse of men. The door and windows were barred, and those inside refused to give admittance. The fugitives were determined to fight, and to die, rather than to be taken back to slavery. Margaret, the mother of the four children, declared that she would kill herself and her children before she would return to bondage. The slave men were armed and fought bravely. The window was first battered down with a stick of wood, and one of the deputy marshals attempted to enter, but a pistol shot from within made a flesh wound on his arm and caused him to abandon the attempt. The pursuers then battered down the door with some timber and rushed in. The husband of Margaret fired several shots, and wounded one of the officers, but was soon overpowered and dragged out of the house. At this moment, Margaret Garner, seeing that their hopes of freedom were in vain, seized a butcher knife that lay on the table, and with one stroke cut the throat of her little daughter, whom she probably loved the best. She then attempted to take the life of the other children and to kill herself, but she was overpowered and hampered before she could complete her desperate work. The whole party was then arrested and lodged in jail.

The trial lasted two weeks, drawing crowds to the courtroom every day....The counsel for the defense brought witnesses to prove that the fugitives had been permitted to visit the city at various times previously. It was claimed that Margaret Garner had been brought here by her owners a number of years before, to act as nurse girl, and according to the law which liberated slaves who were brought into free States by the consent of their masters, she had been free from that time, and her children, all of whom had been born since then -- following the condition of the mother--were likewise free.

The Commissioner decided that a voluntary return to slavery, after a visit to a free State, re- attached the conditions of slavery, and that the fugitives were legally slaves at the time of their escape....

But in spite of touching appeals, of eloquent pleadings, the Commissioner remanded the fugitives back to slavery. He said that it was not a question of feeling to be decided by the chance current of his sympathies; the law of Kentucky and the United States made it a question of property.

 

Source: Levi Coffin, Reminiscences (Cincinnati, 1876).
(Citation from Digital History)

Here are some differences between the story of Sethe and her children in Beloved and the historical life of Margaret Garner: 

• Margaret Garner is described as a mixed race woman, and may have been the biological daughter of John Pollard Gaines (the brother of her later owner, Archibald K. Gaines).  
• Margaret Garner had four children (like Sethe), but at least some historical accounts suggest that three of those children may not have been fathered by Robert Garner. There is some evidence to suggest that Archibald Gaines may have been the father of her younger children. 
• Margaret Garner is described in another account as having a scar on the left side of her forehead and cheek, which she described as being the results of when a “white man struck me.” There’s no evidence that I know of that she had scars on her back, as Sethe does in the novel.
• Margaret Garner escaped with her husband Robert and seventeen other people in January 1856 (part of a “train”). It was an extremely cold winter and the Ohio River had frozen over; the Garner family crossed it on foot. 
• In contrast to the novel, the house where the Garners were recaptured (which belonged to the son of Margaret Garner’s uncle, Joe Kite) was not intended as a permanent home for the family -- they were just staying there temporarily before they could find a more permanent place of safety (others in the party that escaped from Kentucky with them kept moving, and safely went on to Canada).
• Robert Garner was armed and fired shots at the slave catchers and U.S. Marshals that surrounded the house; according to Levi Coffin's account above, Robert Garner wounded one of the marshals. 
• After their arrest, there was a debate as to whether Margaret Garner and her husband should be tried for murder (suggesting that both they and their children were human beings deserving of fundamental rights), or for theft and destruction of “property” under the Fugitive Slave Law. Her legal defense actually wanted her tried for murder, since that would underline her humanity and that of her children. There was also an understanding that even if she were found guilty, she might receive a pardon from the governor of Ohio later. The case became a sensation; hundreds of people crowded into the courtroom for each hearing, with hundreds more on the street. Prominent abolitionist activists were also involved, including especially Lucy Stone. 
• Before she could be tried, officials ruled she could be returned to Kentucky along with Robert and their youngest child (an infant). Later, Ohio officials did get a warrant to re-arrest and extradite Margaret Garner back to Ohio, but A.K. Gaines had left Maplewood and was difficult to locate; he eventually sent the Garners to his brother’s plantation in Arkansas. 
• Margaret Garner died in slavery in 1858 due to typhoid fever. Her husband Robert Garner survived to see the end of the Civil War; he was interviewed about his life in 1870 by a reporter for the Cincinnati Chronicle.

--Amardeep Singh, April 2021 [Updated October 2021]