The tech company, launched in 1976 in a Los Altos garage, revolutionized personal computing - popularizing experimental technologies developed in the Xerox Parc research labs, such as the mouse and graphical user interface.
The company's stock was at $205.98, up 2.2 percent near 1555 GMT.
Although many have doubted Apple's staying power over the years, unlike many hardware makers the company has ridden the elegance and functionality of its devices.
The peak reached Thursday seemed unimaginable in 1997 when Apple teetered on the edge of bankruptcy, with its stock trading for less than $1. By previous year, its sales had grown more than 11-fold to US$229 billion - the fourth highest in the S&P 500 - and net income had mushroomed at twice that rate to US$48.4 billion, making it the most profitable publicly-listed United States company.
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However, because the company readjusted its share count due to buybacks at the close of Q3, Apple's stock price actually needed to hit about $207.05 per share before it can claim the title as the first trillion dollar company.
The stock has been rising since Tuesday when it reported better than expected results for the three months to June. Since 1980, IBM, Exxon Mobil, General Electric and Microsoft have also alternated as the largest publicly listed U.S. company.
One of five USA companies since the 1980s to take a turn as Wall Street's largest company by market capitalisation, Apple could lose its lead to the likes of Alphabet or Amazon.com if it does not find a major new product or service as global demand for smartphones loses steam.
Stock market veterans note that the first trillion-dollar public company - if only briefly - appears to have been PetroChina Co.
Amazon, Google owner Alphabet and Microsoft have all rallied to near record highs this year, too.