What just happened? Remember when Apple became the first US company to pass the $1 trillion market valuation barrier? Now, the iPhone maker has reached another milestone: the first American firm to boast a $1.5 trillion market capitalization.

Back in 2018, Apple's stock price got a boost after its revenue grew 17 percent year-over-year. The increase led its market capitalization to reach an amazing $1 trillion. A month later, Amazon became the next US tech giant to join the trillion-dollar club. Since then, Microsoft and Alphabet have also seen their market caps pass $1 trillion.

Despite the world fearing a recession that could surpass the great depression, Apple's stock has jumped from $307 around a month ago to $354 yesterday. Investors have welcomed excitement over the upcoming iPhone 12 series, strong sales in the App Store, and news that Apple could announce ARM-based Macs at WWDC later this month.

Market caps are calculated by multiplying the share price by the total number of a company's outstanding shares. Apple has been aggressively buying back some of its own stock in recent years to reduce its vast cash reserves, but this is accounted for.

Sources say that Apple wants to move away from Intel's chips due to concerns that performance gains between generations are diminishing. They added that ARM-based chips have shown "sizable improvements" over Intel's offerings, especially when it comes to graphical power and apps that use AI. We could see these ARM-powered Macs as soon as next year.

Anticipation over the next generation of iPhones is also boosting Apple's shares. The iPhone 12 is rumored to feature ProMotion high-refresh-rate displays, 3x telephoto zoom, and improved Face ID. They'll also mark Apple's entry into the 5G market.

Apple might have been the first US firm to hit $1.5 trillion, but Microsoft is close behind with a market cap of $1.4 trillion. Amazon is valued at $1.32 trillion, while Alphabet is the last of the big four, sitting at $1 trillion.