[3] The house is surrounded by a large estate which, at the time of the 7th Earl of Carlisle, covered over 13,000 acres (5,300 ha) and included the villages of Welburn, Bulmer, Slingsby, Terrington and Coneysthorpe.

[5] While attending Girton College during the early Edwardian era, Lady Dorothy Georgiana Howard, the daughter of the 9th Earl and "Radical Countess" of Carlisle, befriended six of her fellow students, including the future archaeologist Gisela Richter and future candidate for Roman Catholic Sainthood Anna Abrikosova.

Henry 'Chips' Channon, the diarist and future Conservative MP, visited Castle Howard in August 1923 and recounted in his diary that 'The house is uncomfortable in the extreme and is badly kept up.

Channon added that 'The galleries are reminiscent of the Vatican with their hundreds of busts and statues of emperors and gods.

The great library is an enormous narrow red room the length of the house and is hung with enough paintings to found a museum.

[8] The 3rd Earl of Carlisle first spoke to William Talman, a leading architect, but commissioned Vanbrugh, a fellow member of the Kit-Cat Club, to design the building.

[3] Vanbrugh's design evolved into a Baroque structure with two symmetrical wings projecting to either side of a north–south axis.

All are exuberantly decorated in Baroque style, with coronets, cherubs, urns and cyphers, with Roman Doric pilasters on the north front and Corinthian on the south.

Although the complete design is shown in the third volume of Colen Campbell's Vitruvius Britannicus, published in 1725, the West Wing was not yet started when Vanbrugh died in 1726, despite his remonstration with the Earl.

[10] According to figures released by the Association of Leading Visitor Attractions, over 269,000 people visited Castle Howard in 2019.

The house is prominently situated on a ridge and this was exploited in the development of an English landscape park, which adjoins and opens out from the formal garden.

[15][16] Located on the estate, but operating separately from the house and gardens and run by an entirely independent charitable trust, is the 127 acres (51 ha) Yorkshire Arboretum.