Four private equity firms which became majority owners of a US railroad company 20 years ago are finally set to cash in their investment and will make at least a 20 times return on their money.

The companies, which own a 30% stake in Dakota Minnesota & Eastern Railroad Corporation between them, are selling out after the company was sold to rival Canadian Pacific Railway. The agreed $1.48bn (€1.1bn) sale comes amid booming demand for oligopolistic assets from financial investors, including Warren Buffett, who lives in the next state down from the Dakota railroad, and Fortress.