Microsoft co-founder Bill Gates is still America's richest man, taking the top spot in the Forbes 400 list for the 20th-straight year with a net worth of $72 billion.
Investor Warren Buffett, the head of Berkshire Hathaway, remains in second place with $58.5 billion, while Oracle co-founder Larry Ellison stays third with $41 billion.
Brothers Charles and David Koch, co-owners of Koch Industries, stay tied for fourth with $36 billion each.
Forbes says America's super rich continued to increase their wealth over the past year, with the 400 people on the annual list posting a combined net worth of $2 trillion, up from $1.7 trillion a year ago. That marks their highest combined value ever.
Forbes attributed the growth to strong stock and real estate markets.