Microsoft was the first company to exceed a $600 billion market capitalization, reaching the milestone in 1999.
Microsoft’s valuation surged during the late-1990s technology boom, when investors placed enormous value on its Windows operating system and Office productivity software. In December 1999, its market capitalization exceeded $600 billion, making it one of the most valuable companies ever recorded at that time.
The figure should not be compared directly with modern valuations without considering inflation, share counts, and changing market conventions. Microsoft’s market value later fell during the dot-com bust. The company eventually entered a new growth phase through cloud computing, enterprise software, and subscriptions, but the 1999 record belongs to the era when personal-computer software dominated technology investing.