Microsoft was the first company to reach a $600 billion market capitalization at the end of 1999.
The milestone came during the technology boom of the late 1990s, when investors placed exceptionally high valuations on major software and internet businesses. Microsoft’s Windows operating system and Office productivity software gave it a dominant position in personal computing, while its expanding commercial software business supported rapid growth.
Microsoft’s share price rose sharply during the 1990s, helping the company become the world’s most valuable publicly traded business for a period. Its valuation later declined during the dot-com crash and remained below its late-1990s peak for many years.
The $600 billion figure is a historical market-cap milestone, not a measure of annual revenue or cash held by Microsoft. Market capitalization changes daily with the share price, so rankings among the world’s richest companies can shift even when a company’s underlying operations change more slowly.