Based on the first twenty-seven chapters of Abraham Lincoln: The Prairie Years, Sandburg's Abe Lincoln Grows Up presents the first twenty years of Lincoln's life, from his birth in a log cabin, through the migrations of the Lincoln family in Kentucky, Indiana, and Illinois, until the time that Abe gathers his few belongings and leaves home for New Salem, in search of an education and a better life. This is a classic example of the American success story: a boy born and raised in poverty, with many hardships and very little formal education, struggles to make something of himself. Although the story ends just as Lincoln leaves home, all readers know that he is destined to become one of the best known and most loved presidents of the United States.

This biography offers an outstanding depiction of American frontier living, describing the wilderness, the farms, and the settlements; Sandburg shows how the settlers built their houses, grew their crops, and battled Native Americans. He faithfully recounts their joys, such as a wedding feast with "bearmeat, venison, wild turkey and ducks," and their sorrows, such as the epidemics of strange illnesses that took the lives of many people, including Lincoln's mother.

Following Lincoln down the Ohio and Mississippi rivers on a flatboat to New Orleans, the reader also glimpses the world beyond the frontier. Sandburg includes many interesting sidelights, such as Andrew Jackson's presidential campaign, that place Lincoln's early life in historical context.