Conversation so far:
what happened to Andrew Carnegie in 1901?
public attention was turned from the shrewd business acumen to the public-spirited way in which Andrew Carnegie devoted himself to utilizing it on philanthropic projects.
were andrew carnegie's philantropic projects a success?
the establishment of public libraries was among Andrew Carnegie's many sucessful philanthropic efforts.
what did Andrew Carnegie do as a business magnate?
Andrew Carnegie built Pittsburgh's Carnegie Steel Company
what was Andrew Carnegie's greatest accomplishment?
After selling Carnegie Steel, Andrew Carnegie surpassed John D. Rockefeller as the richest American for the next several years.

Question: what is the most important fact mentioned in the article?
Self-contained rewrite: what is the most important fact mentioned in the Andrew carnegie article?