“Mr. Sandburg possesses a powerful imagination, which plays over and about his realistic themes and constantly ennobles them. …strikes, and factories, and slaughter-houses, and railroad trains, all take on a lyric quality under his touch. …When Carl Sandburg left college, he was no longer an unskilled labourer, working with his hands. He was a thinking man, with a brain charged with ideas and emotions, determined to do his part in bringing about the millennium. For Carl Sandburg… is a revolutionary; he must push the world to where he is convinced it ought to be. …again and again, he deserts the seer's mountain peak for the demagogue's soap-box. …Mr. Sandburg is like a man striving to batter down a jail with balls of brightly coloured glass. …Whether constant preoccupation with disease is a healthy form of literature, whether it acts as a curative, is open to question. But we can surely say that to be curative the disease must be treated unsentimentally and truly. Mr. Sandburg has aimed at doing this, has striven hard to do it. For this, one honours him above his fellows. For this, and the spirit of beauty which pervades his work.”

"Edgar Lee Masters and Carl Sandburg," Tendencies in Modern American Poetry http://books.google.com/books?id=UgZaAAAAMAAJ (1917).