Amazon.com Inc., the e-commerce giant that has changed how much of the world shops for books, toilet paper and TVs, has hit yet another milestone.

Amazon stock hit $1,001.20 shortly after Tuesday's opening bell, up about 40 percent from a year ago and more than double the 15 percent gain of the S&P 500 Index in the same period.

Investors are thinking about how much further Amazon can grow as it tries to replicate its U.S. success abroad, Bloomberg reported.

The $1,000 share price also puts Amazon's market value at about $478 billion, double that of rival Wal-Mart and more than 15 times the size of Target, the Associated Press reported.

The shares will likely push even higher since Amazon is growing so quickly in massive global industries that show no signs of slowing, as shopping habits change and businesses rethink how they deploy technology, said John Blackledge, analyst at Cowen and Company LLC, who recently upped his Amazon price target to $1,125 a share.

"There’s a long runway there," he told Bloomberg. "The markets Amazon is playing in with global retail and cloud computing are just massive. Things continue to go well and investors are looking for more upside."

Meanwhile, only 14 other U.S. stocks trade above $1,000 per share, FactSet reported, and the only other tech company in the club is Priceline Group, currently trading around $1,865. Amazon also is more than four times more valuable than those other 14 companies combined, CNBC.com explained. Meanwhile, Alphabet’s Class A shares are currently trading above $990.

Amazon has come a long way since its start in 1995, when it mostly sold books. The Seattle company now sells just about anything, from groceries to small appliances, and has been blamed for taking business away from department stores, supermarkets and clothing retailers.

“Amazon has split three times since its IPO in 1997. In 1998, it issued a two-for-one stock split. In January 1999, it issued a three-for-one stock split and, in September 1999, it issued a two-for-one split. When Amazon hit $1,000, it's technically the equivalent of a $12,000 share price in today's terms,” CNBC reported.

For its part, Amazon's ventures far beyond online retail, from cloud computing to movie making, are raising questions among corporate strategy experts about its focus, Reuters reported.

The Seattle-based company wowed Wall Street recently with a 23 percent jump in sales, pushing its shares to an all-time high. But there are concerns that if blockbuster growth stops, investors may come to regard the company more like a conglomerate stock - worth less than the sum of its pieces, Reuters reported.

"High growth covers a lot of sins," said Harry Kraemer, a partner at private equity firm Madison Dearborn Partners and a professor at Northwestern University's Kellogg School of Management.

Investors also put more value in Amazon’s web traffic and delivery network than they do in Wal-Mart’s vast store presence because online spending will grow more than four times faster than overall retail spending this year as shoppers continue to shift from stores to websites, Bloomberg reported, citing EMarketer Inc.

The world’s largest online retailer is dominating e-commerce with its $99-a-year Amazon Prime subscription, which includes delivery discounts, music and video streaming and photo storage that keep shoppers engaged with the website. Amazon had 80 million Prime subscribers in the U.S. as of March 31, an increase of 38 percent from a year earlier, according to Consumer Intelligence Research Partners. Prime memberships help lock in loyalty, which is critical as competitors such as Wal-Mart enhance their e-commerce offerings to slow Amazon’s momentum, Bloomberg reported.

Amazon has been tackling retail one category at a time, disrupting bookstores and electronics stores first and more recently pushing into apparel and groceries. Its rise has coincided with the decline of prominent retail chains such as Macy’s Inc. and Sears Holdings Corp., which have shuttered stores and laid off workers in response to declining sales. Shopping malls have resorted to hosting concerts and carnivals in empty parking lots to keep customers coming.

Amazon’s rise has made its founding Chief Executive Officer Jeff Bezos the world’s second wealthiest person, behind only Microsoft Corp. co-founder Bill Gates, according to the Bloomberg Billionaires Index. His ascendancy has won praise from fellow self-made billionaires Warren Buffett and Mark Cuban, owner of the Dallas Mavericks and judge on the television show "Shark Tank."

“Amazon is worth far more than $1,000 a share,” said Cuban, an Amazon investor. “Consumers always want things at lower prices delivered faster. Amazon uses data better than anyone to achieve those goals for everything it sells. They have a chance to be the most dominant company in the world.”

(Newsmax wire services, the Associated Press, Reuters and Bloomberg contributed to this report).