Microsoft became the first public company valued at $500 billion.
The milestone occurred in 1999 during the late-1990s technology boom, when investors placed exceptionally high values on software and internet-related businesses. Microsoft’s Windows operating system and Office productivity suite gave it a powerful position in personal computing and generated substantial profits.
Microsoft’s rise was built earlier in the decade through agreements that helped place MS-DOS and Windows on IBM-compatible personal computers. The company’s software became a standard platform for homes and offices, supporting recurring sales and a large developer ecosystem.
The $500 billion figure refers to market capitalization, not annual sales or the amount of money Microsoft had in the bank. Market-cap records from the dot-com era are also distinct from later trillion-dollar milestones, which reflect decades of stock-price changes, share repurchases, and business expansion.