Daniel Wolff's book, How Lincoln Learned to Read, considers the lives of 12 great Americans, from Abigail Adams to Sojourner Truth, and explores early influences on character. Here's a sample.
His older brother, a printer; himself.
He was a Boston Latin dropout, but he came from a literate family and spent his teenage years engrossed by books and writing pseudonymously for his brother's newspaper.
The usefulness of rebelling—revolting, even—against traditional institutions, and how to communicate with the public.
"He'd developed a style, making up for a lack of poetic ability with a sly sense of humor and developing the condensed, pointed edge of the aphorism… a method particularly suited to speaking out against old institutions."
His mother, who'd gone to school, and later his stepmother, who brought books with her to the frontier; himself.
A few months each winter in a frontier schoolhouse during his boyhood; constant reading and thinking; a determination to translate complex ideas into simple statements.