Shares of Apple Inc. scaled a new all-time peak on Monday, spurred by the anticipated September launch of the new iPhone, coupled with rumors of a smaller iPad and a more feature-rich Apple TV.

Apple closed at US$665.15, up 2.6% on the day. Apple's market value surpassed US$623bn, eclipsing the record of US$618.9bn set by Microsoft Corp. during the height of the dot-com bubble in 1999.

Apple was valued at less than US$10bn as recently as 2004, and at US$100bn just three years ago. Apple has crossed the US$400bn, US$500bn and US$600bn milestones all in 2012, with the stock soaring 64% year-to-date.

Apple shares are up almost 9% this month as Wall Street bets on the Sept. 12 rollout of the latest version of the iPhone.

At Friday’s close, Apple represented 4.73% of the S&P 500 index, with a market capitalisation of US$607.54bn, according to a senior index analyst at S&P Dow Jones Indices. 

Apple is on pace to be the world's largest technology company in terms of sales by the end of the year, and it's among the most profitable companies in the world.

Microsoft, however, retains the title of history's most valuable company if its 1999 peak value of ~US$621bn were to be adjusted for inflation. In 2012 dollars, Microsoft's all-time-high would have amounted to US$851bn.