The answer is:
A. Andrew Carnegie.
Andrew Carnegie started out dirt poor, yet eventually found his big break in the steel industry and helped lead the expansion of the industry in America. When he was older, he gave a massive amount of his vast fortune made from the steel industry away to charities (alongside other acts of philanthropy), funded the construction of over 3,000 libraries, and heavily invested in education, along with so many other amounts of contributions to American society as we know it. By the time of Carnegie's death, he was one of the richest people ever with a net worth of $307 billion (adjusted for inflation).