The annual list ranked companies by their revenue in the 2018 fiscal year.
"FORTUNE 500 companies represent two-thirds of the U.S. GDP with $13.7 trillion in revenues, $1.1 trillion in profits, $22.6 trillion in market value, and employ 28.7 million people worldwide," the company said in a statement.
The second-largest company was oil giant Exxon Mobil, with Apple moving up one spot to third.
In a shift of corporate wealth westward, California-based FORTUNE 500 companies "generated the most aggregate revenue ($1.6 trillion), earned the most aggregate profits ($256 billion), and are valued the most in market cap ($5.5 trillion)," the statement said.
In fact, five of the six most valuable companies were tech giants, with Microsoft, Apple and Amazon each reaching valuations of $1 trillion in the past year.
Also, for the first time, there were 33 female-led companies on the list — the highest number of women CEOs ever. Last year there were 24 on the list.
Here are the top 10 companies ranked by Fortune.?
1. Walmart 2. Exxon Mobil 3. Apple 4. Berkshire Hathaway 5. Amazon.com 6. UnitedHealth Group 7. McKesson 8. CVS Health 9. AT&T 10. AmerisourceBergen