An American worth less than $1.55 billion could not land on  this year's "The Forbes 400," the annual ranking for the richest people in America. The cut-off increase from last year's $1.3 billion disqualified 113 poor billionaires for this year's list.

Bill Gates once again lorded over his fellow wealthy Americans for the 21st consecutive year with a healthy $81 billion, up $9 billion from 2013. He outpaced Warren Buffet ($67 billion), Larry Ellison ($50 billion) and the Koch brothers' Charles and David (each worth $42 billion) to round out the top five.

Michael Bloomberg ($35 billion) managed to slide into the No. 8 spot between the Walton family members. The Walmart heirs were led by Christy Walton, who married into the family and inherited her husband's fortune after his death in 2005. Her in-laws Jim, Alice and S. Robsen took up the remaining three spaces.

A majority of list contenders (276) were self-made billionaires compared to the 58 who inherited their wealth. Another 66 billionaires inherited a portion of their wealth but continue to increase their value.

Investments, technology and food and beverage industries dominated the list. Celebrities like George Lucas (115), Steven Spielberg (152) and Oprah Winfrey (209) managed to make their ways onto the list.

The list of 400 uber-rich Americans produced only 47 women, one fewer than last year. The other women to crack the top 20 was Jacqueline Mars of the Mars candy makers. Elizabeth Holmes, founder of Theranos, was the youngest woman at age 30 to make the list in the No. 110 spot.

Facebook co-founders Mark Zuckerberg and Dustin Moskovitz, both 30, ranked as the youngest billionaires. Moskovitz is a few days younger than Zuckerberg, who still is worth more at $34 billion compared to Moskovitz's $8.1 billion.

The combined net worth of the entire list was $2.29 trillion, up from $2.02 trillion in 2013. A total of 27 people dropped off the list from last year, and six died.