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's the top 10:
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
The Walt Disney Co., the parent company of ABC News, ranked 53rd.
For the complete list, click here.