Microsoft was the first company to reach a US$500 billion market capitalization during the 1990s dot-com boom.
Microsoft crossed a market value of US$500 billion in December 1998. The milestone reflected investor expectations for the company’s dominant Windows operating system, Office productivity software, and growing role in the rapidly expanding personal-computer industry.
At the time, Microsoft was led by co-founder Bill Gates and chief executive Steve Ballmer. Its stock had risen sharply during the technology boom, making it the most valuable publicly traded company for periods in the late 1990s. The company’s market capitalization later moved substantially as the dot-com bubble inflated and then collapsed.
The $500 billion figure is a valuation, not a revenue total. Microsoft’s annual revenue was far smaller because market capitalization represents what investors collectively paid for its shares. Comparing old records also requires care because stock splits and changing share counts affect the share price associated with a given valuation.