One of the earliest fracking pioneers, Harold Hamm started Continental Resources in 1967. The oil company is the largest leaseholder and producer in the Bakken oil field in North Dakota and Montana.

Having taken it public in 2007, Hamm and his five children opted to take the company private again in 2022, in a deal worth $27 billion.

Their estimated net worth is $18.5 billion, making the Hamm clan the richest family in the state – and overtaking the Oklahoma-based Judy Love and her family, who are the owners of Love’s Travel Stops and Country Stores.