Richest: Warren Buffett — $144 billion

The finance and investments industry has been the biggest maker of fortunes. Most of the wealthiest individuals in this category are founders of hedge funds, mortgage lenders, VC, and investment firms.

Some are heirs to founders, such as the grandchildren of Fidelity founder Edward Johnson II.

Richest: Elon Musk — $908 billion

Technology has been a massive maker of fortunes; the nine richest in this category are wealthier than Warren Buffett.

Many are founders of big-name tech companies, as well as software and computer hardware firms. The AI boom has brought several newcomers to the list, including OpenAI cofounder and president Greg Brockman.

Richest: (Tie) Jacqueline and John Mars — $50.3 billion

From Chick-fil-A to Tito's Vodka, there are plenty of household-name brands in this category.

Others made their fortunes in the non-consumer parts of the food and beverage industry. These include J. Christopher Reyes and Jude Reyes, who cochair the food and beverage distribution firm Reyes Holdings, or Harry Stine, who made his fortune licensing soybean and corn genetics.

Richest: Rob Walton & family — $132 billion

Like food and beverage, household names dominate the fashion & retail category. Walmart alone is listed as the source of wealth of eight people in this industry.

Other sources of retail wealth are less obvious. Jimmy and Bill Haslam's fortunes largely derive from the truck stop chain Pilot Flying J, which their father founded.

Richest: Lyndal Stephens Greth & family — $30 billion

Oil tycoons and their families make up the bulk of this list. And it's not just those with stakes or roles in companies involved in production, but also pipelines and refineries.

Richest: Stephen Ross — $21.5 billion

America's wealthiest real-estate magnates built their fortunes through all kinds of properties. Jeff Greene, for example, made billions investing in credit default swaps tied to subprime mortgage-backed securities before the financial crisis.

With an estimated net worth of $7 billion and much of his wealth tied to real estate, President Donald Trump is also included in this category.

Richest: Rupert Murdoch & family — $25 billion

Legacy media, such as cable and satellite television, continue to dominate this category. However, some billionaires built their fortunes through other kinds of media, including Gabe Newell, who cofounded video game developer Valve.

Movies have minted others, such as award-winning director Steven Spielberg and "Star Wars" creator George Lucas.

Richest: Stanley Kroenke — $27.6 billion

For many people in the sports category, team ownership is more of a second act, rather than the original source of their wealth.

For example, before they bought teams, Arthur Blank cofounded Home Depot, Stephen Bisciotti made his fortune in talent management, and Arturo Moreno made his money from billboard advertising.

There are some exceptions, such as Michael Jordan, whose basketball career was the origin of his wealth.

Richest: Thomas Frist, Jr. & family — $33.6 billion

Aside from the category's richest entry, Thomas Frist Jr. and family, whose wealth comes from hospitals, most of the others made or inherited their fortunes in pharmaceuticals, medical devices, and medical equipment.

One, Patrick Soon-Shiong, developed the chemotherapy drug Abraxane.

Richest: Steven Rales — $8.7 billion

Manufacturing spans a variety of industries, from packaging materials to defense.

Some big fortunes come from everyday products you might not expect. Cleaning products alone account for four people on the list, all of whom are heirs to SC Johnson, whose products include Windex and Glade.

Richest: Micky Arison & family — $11.5 billion

Aircraft leasing, cruises, and self-storage are just some examples of services that have turned people into billionaires.

Lucrative service companies aren't necessarily the most glamorous. Gary Rollins, for example, is executive chairman emeritus of pest control firm Rollins, which was founded by his father.

Richest: Ernest Garcia, II — $24.3 billion

In the US, automotive fortunes are less about manufacturing cars and more about selling, servicing, and moving them.

Forbes 400 member Dan Friedkin, for example, owns Gulf States Toyota, while Shahid Khan owns auto parts supplier Flex-N-Gate.

Richest: Julia Koch & family — $84.6 billion

Diversified means fortunes that don't neatly come from one industry. Members of the Koch family, which has stakes in the conglomerate Koch, dominate this segment.

Richest: Brad Jacobs — $13.3 billion

The businesses that move products through the supply chain are among the most essential to day-to-day life, and can be worth billions.

For example, Johnelle Hunt, who cofounded transportation and logistics firm J.B. Hunt Transport Services, is worth $6.6 billion.

Richest: Diane Hendricks — $23.6 billion

All three members of the Forbes 400 in the construction and engineering industry are self-made billionaires.

Diane Hendricks cofounded building-supply distributor ABC Supply with her late husband, Ken Hendricks. Mike Hollingshead founded concrete maker Smyrna Ready Mix, while Robert Clark founded construction firm Clayco.

Richest: Miriam Adelson & family — $33.5 billion

With just two members categorized in the Forbes 400, gambling and casinos are the smallest category.

Miriam Adelson's late husband, Sheldon Adelson, was the founder of casino company Las Vegas Sands, while Jon Yarbrough founded casino producer Video Gaming Technologies.

Phil Ruffin, who Forbes categorized as diversified, made his wealth from a mix of casinos and real estate.