The December 5, 1936 Chicago Daily Tribune ran a short article titled, "Sinclair Lewis Put First As Author to be Read Until 2000." Below is the article in its entirety. I've added links to the Wikipedia page for each author mentioned.
Sinclair Lewis is the American author of the present day whose books are most likely to continue to be read in the year 2000, is the verdict of subscribers to The Colophon, a book collectors' quarterly, who were asked by its editors to vote on the question of literary survival. Only living American authors were included.
Next to Mr. Lewis, whose point score was 332, comes Willa Cather with a point score of 304. These are the only authors who exceed a 300 batting average.
Eugene O'Neill with 292 points and Edna St. Vincent Millay with 205 come next, followed by Robert Frost, 180; Theodore Dreiser, 149; James Truslow Adams, 115; George Santayana, 113; Stephen Vincent Benet, 91, and James Branch Cabell, 90.