SAN FRANCISCO -- Apple on Monday became the most valuable company in history after a surge in its stock price, beating the record set by Microsoft in December 1999.

Apple's stock price topped $660 per share, pushing the company's market capitalization up to $619 billion. The record was previously kept by Microsoft, whose market value peaked on December 30, 1999 with $618.89 billion.

However, accounting for inflation, Microsoft still retains the title by a margin. According to technology news site MacRumors, Microsoft's $618.89-billion market capitalization in December 1999 would be equivalent to roughly $842.5 billion in today in inflation-adjusted terms. Microsoft is now worth $257 billion.

Apple is expected to introduce iPhone 5 next month and a smaller and cheaper iPad, which has propelled the company's stock to new highs recently.