How did Abraham Lincoln compose his famous speeches? A historian at Knox College in Galesburg, Ill., Douglas Wilson, has won the Lincoln Prize for examining the process by which the 16th president crafted prose that is among the most memorable in American history. In April, Mr. Wilson will receive $50,000 and a bronze cast of Augustus St. Gaudens’s Lincoln sculpture in recognition of his book “Lincoln’s Sword: The Presidency and the Power of Words” (Knopf).

In “Lincoln’s Sword,” Mr. Wilson has examined drafts of composition, refinement, second thoughts, and recasting in which Lincoln transformed ordinary thoughts into immortal speech. Mr. Wilson is an excellent “close reader,” said a juror of the prize, John Simon, who is a professor at Southern Illinois University, Carbondale.

The co-director of the Lincoln Studies Center at Knox College, Mr. Wilson said his book grew out of the process of transcribing the most important of Lincoln works for the Library of Congress, which impressed upon him Lincoln’s literary craftsmanship. “Just about everything we have of Lincoln shows him revising — that caught my attention.”

Ascending to the presidency at the age of 52, Lincoln was an accomplished, self-taught writer. But the pubic (including his political opponents) had the strong impression of him as a rube with little education, a yokel who told jokes. “This means he came to the presidency with a hidden asset,” Mr. Wilson said.

Mr. Wilson said the public’s idea is that if a speech like the Gettysburg Address is short, it does not take long to write. He said the speech was in fact an example of Lincoln’s practice of “pre-writing.”

Mr. Wilson believes that Lincoln knew if he wrote something short, hundreds of thousands of people would get a chance to read it in newspapers.

He argues that it took years before Lincoln’s famous lines became imprinted in the public imagination. After Lincoln was shot, even critics embraced him and realized that his words were memorable.

The Lincoln & Soldiers Institute at Gettysburg College awards the Lincoln Prize for the year’s best book on Abraham Lincoln and the Civil War. A three-member Lincoln Prize jury winnowed down the list from about 119 books. The business leaders and philanthropists Lewis Lehrman and Richard Gilder, an investor in this newspaper, endowed the prize. The chairman of its prize board, Gabor Boritt, is himself the winner of the Barondess/Lincoln Prize, which the New York Civil War Round Table is awarding tonight.

Mr. Wilson previously won the Lincoln Prize in 1999 for “Honor’s Voice: The Transformation of Abraham Lincoln.” Mr. Wilson is completing an annotated edition of the Lincoln-Douglas debates, which is fitting since the fifth debate occurred at Knox College, where he teaches.

A Lincoln scholar, Harold Holzer, said that in parsing Lincoln’s prose, Mr. Wilson had managed to trace the growth of a great American writer. He summed up the achievement thus: In examining the Lincoln’s texts with words crossed out, Mr. Wilson “has done more with carets than anyone since Elizabeth Taylor.”