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."
Amazon crossed the mark five weeks after Apple reached $1 trillion in early August after posting a strong quarterly report.
Despite falling from session highs, Amazon posted its seventh straight day of gains. At its peak Tuesday, the stock had picked up $72 billion in market value in the last seven days of trading. That increase is larger than the market value of more than 80 percent of S&P 500 constituents, and is roughly the size of Starbucks.
Amazon stock has gained more than 70 percent in 2018 and has more than doubled in the last 12 months. That dwarfs gains by the overall market, with the S&P 500 index gaining 8 percent this year and 17 percent in the last 12 months.