Microsoft became the first publicly traded business valued at US$500 billion in 1999.
Microsoft reached a market capitalization of roughly US$500 billion during the technology-stock boom of 1999. The company’s dominant Windows operating system and Office productivity software gave it enormous influence over personal computing, while its growing internet and enterprise businesses attracted further investor interest.
Microsoft had gone public in 1986, and its market value expanded dramatically as personal computers became standard tools in homes and workplaces. The company’s stock later experienced a prolonged decline after the dot-com era, before cloud computing and the Azure platform helped drive a new period of growth.
Historical market-cap records depend on the definition used: an intraday peak, a closing value, or an inflation-adjusted figure can produce different comparisons. The US$500 billion milestone is generally cited as a nominal market capitalization reached during the 1999 technology boom.