A United States ranching family has bought a Canterbury station for $12.5 million.

Calvin Erdman, 84, and his sons, Sumner and Christian, acquired the 3418-hectare beef and sheep farm known as Big Ben station, 40 kilometres from Methven, after approval from the Overseas Investment Commission in September.

The low profile Erdman family already owns the Coleridge Downs, Dry Acheron and Annavale stations and plans to integrate Big Ben into its existing farm operation, run by manager Tony Plunkett.

Under an investment plan for all the land it now owns around Lake Coleridge, the family proposes protecting about 1500ha with a QEII open space covenant or conservation covenant and extending the existing walkway on Dry Acheron to create a loop track that would cross Big Ben station.

Calvin Erdman, whose mother was a rancher in Wyoming, bought a 16,000ha ranch on Maui, Hawaii in 1963. Media star Oprah Winfrey recently bought a 400ha ranch next door.

Some of Erdman's original ranch was sold off to a resort and a subdivision and 4451ha has been placed under the control of a trust to protect its status as open farm land. Native forest on the land has also been fenced off and enhanced.

The Erdmans have diversified farming on the remaining 7284ha by setting up a vineyard and augmenting the cattle herd with sheep, goats and elk.

The first wind turbine on the land started construction two years ago and an eight turbine wind facility is planned.

The sellers of Big Ben station are Philip Wareing and related interests. Wareing has property, transport and farming businesses in Mid Canterbury.