Gates

Bill Gates built his fortune by co-founding Microsoft in 1975 with Paul Allen and developing MS-DOS, which became the backbone of IBM’s first PCs, propelling Microsoft to dominance.

Gates then led the company to global success with Windows, which by the 1990s powered over 90% of personal computers worldwide, and the Office Suite, which became an industry standard.

By holding around 45% of Microsoft’s stock after its 1986 IPO, Gates saw his wealth surge as the company’s market cap exploded.

Even after stepping down as CEO in 2000, he diversified through Cascade Investment, channeling profits into railroads, energy, and hotels, helping preserve and grow his wealth beyond tech.