Facebook CEO Mark Zuckerberg returned to the list's top 20 after dropping out the year before. His net worth of $19 billion earned him the No. 20 spot.
Facebook co-founder Dustin Moskovitz also made the list, at No. 85,with a net worth of $5.2 billion. At age 29 and just a few days younger the Zuckerberg, Moskovitz ranks as the youngest member of the list.
On the flip side, the oldest person on the list is 98-year-old David Rockefeller Sr. at No. 193 with a net worth of $2.8 billion.
A total of 20 new people joined the rankings, including Richard Yuengling Jr. of Pennsylvania beer maker D.G. Yuengling & Son, who ranked at No. 371 with $1.4 billion.
Twenty-eight people dropped off the list, including six who died. Those now falling short of the cut include energy tycoon T. Boone Pickens at $950 million, Graham Weston of Rackspace Hosting Inc. at $920 million and Washington Redskins owner Dan Snyder at $1.2 billion.
A total of 48 women made the list including Hyatt Hotels heir Jennifer Pritzker at No. 327. Formerly known as James Pritzker, she's the list's first transgendered member.
According to Forbes, the 400 people on the annual list posted a combined net worth of $2 trillion, up from $1.7 trillion a year ago. That marks their highest combined value ever.
Meanwhile, the average net worth of the list's members rose to $5 billion, also the highest ever, up from $4.2 billion in 2012. Net worth grew for 314 members and fell for 30, Forbes said.
The increases aren't surprising, given that net worth for America's wealthiest people has risen in the years since the financial crisis, widening the gap between the exceptionally well-to-do and the rest of the country.
According to a study of Internal Revenue Service figures released last week, the top 1 percent of U.S. earners collected 19.3 percent of household income in 2012, their largest share in IRS figures going back a century.