Shares of the e-commerce giant rose 1.9 percent to a high of $2,050.50 in morning trading. The stock needed a price of $2,050.27 to reach the $1 trillion mark, based on an outstanding count of 487,741,189 shares in the company's most recent quarterly report in July.
By Tuesday's close, the stock had fallen to $2,039.51 and a market value of roughly $995 billion.
Analysts cite the company's ever-diversifying portfolio as a value driver. Last year, Amazon launched into the grocery industry with its purchase of Whole Foods Markets. It is rounding out its hardware and logistics segments with last-mile deliveries, and it's pushing forward in advertising to challenge Facebook and Google.
"They have given investors confidence that they can go and disrupt markets just like they've done with retail," Loup Ventures' Gene Munster told CNBC's "Squawk Alley" after the milestone stock move.
Amazon has posted particularly impressive growth in Amazon Web Services. The business segment grew nearly 50 percent in the second quarter.
"Yes, Amazon did really well in online retail, but then the stock gapped up when they showed that they could become successful in cloud," RBC Capital Markets analyst Mark Mahaney told CNBC. "It's almost like the ticker changed from AMZN to AWS."