First Page of Lincoln's Handwritten Autobiography
He wrote it in the first person, using fewer than 650 words to summarize his life to that point. Those few plain-spoken words convey his honesty and humility better than anything I have ever read. His description of himself is typical of the tenor of his story:
If any personal description of me is thought desirable, it may be said, I am in height, six feet, four inches, nearly; lean in flesh, weighing, on an average, one hundred and eighty pounds; dark complexion, with coarse black hair, and grey eyes.
The only part of his account which betrays any sense of pride comes when he describes his defeat by Peter Cartwright in his first election:
Then came the Black Hawk War; and I was elected a Captain of Volunteers — a success which gave me more pleasure than any I have had since. I went the campaign, was slated, ran for the Legislature the same year (1832) and was beaten — the only time I ever have been beaten by the people. (He won the popular vote against Douglas).
The next year, as the presidential campaign loomed closer, he wrote a second, longer autobiography, this time in the third person. When this autobiography was published in 1905, the preface read:
A SHORT AUTOBIOGRAPHY, WRITTEN IN JUNE, I860, AT THE REQUEST OF A FRIEND TO USE IN PREPARING A POPULAR CAMPAIGN BIOGRAPHY IN THE ELECTION OF THAT YEAR.
(The Autobiography of Abraham Lincoln, p 3). Lincoln's supporters wrote no fewer than three campaign biographies, it isn't clear which one used the 3,500 word autobiography.
Not long after the publication of Howells's biography, Samuel C. Parks asked Lincoln to read a copy of the book and correct any errors in it. Parks later wrote an inscription on the flyleaf of the book:
This life of Lincoln was corrected by him for me, at my request, in the summer of 1860, by notes in his handwriting in pencil, in the margin. It is to be preserved by my children, as a lasting memorial of that great man, and his friendship for me. Samuel C. Parks, Kansas City, Missouri, May 22, 1901.
In 1938 the Abraham Lincoln Association printed a facsimile copy of the book with Lincoln's annotations, and that facsimile can be accessed at the Internet Archive.
Page from Howells's Biography Annotated by Lincoln
If we stretch a point, we can say that Lincoln wrote three autobiographies, two in his own hand, and the third by annotating Howells's biography.