Best writers of 20th century

Not sure what Classic and Modern would mean but here is a list

wait, this is a hopeless task.

Actually I started to write this and figured what is the point.

American literature in the 20th Century is not like Russian Literature in the 19th Century when a list of giants like Gogol and Tolstoy can be listed.

The 20th Century America saw something utterly unique in human history, never had so many people at one period had an opportunity to write and publish in a single language to such an audience, and the result is a mass of authors of quality without precedence.

In vast fields from novels to poems, criticism, essays, Sci Fiction and highly experimental genre last numbers of men and women created massive innovative work.

One would be better off trying to simply focus on regions, say the top California, New York, New England, Southern, and Midwestern authors, and even then it would be difficult. Frankly to think of all the great writers from New York of SF is beyond me.