Three generations of Sykes built the fortune that built the house. William Sykes migrated from Cumberland in the sixteenth century and prospered as a cloth trader. Daniel moved into Hull shipping. Richard cornered a piece of the Baltic pig-iron trade. By 1751 the family had enough money to demolish the medieval manor at Sledmere and start over, and Sir Richard Sykes did exactly that, raising a new Georgian house in Nottinghamshire ashlar on an H-shaped plan three storeys tall. He planted twenty thousand trees on the bare Wolds around it, an act of imagination as well as landscape design. The trees softened a chalk country that had carried sheep for centuries and little else, and they framed every approach to the house his successors would inherit.

Sir Christopher Sykes, the 2nd Baronet, expanded everything his uncle had begun. He bought up land, enclosed huge tracts for cultivation, planted twenty-five hundred more acres of trees, and moved the entire village of Sledmere out of his sightlines. He added two wings to the house and hired Joseph Rose, the most celebrated plasterer of the age, to decorate inside. Outside, in 1777, he engaged Lancelot Capability Brown to lay out a 960-acre park. The plan survives in the house itself, drawn on paper that Christopher kept. By the time he died in 1801 Sledmere held nearly thirty thousand acres of estate around a mansion set in two hundred acres of designed landscape, and the plasterwork inside had been called the finest in England.

Of all the spaces in the restored house, the Turkish Room is the strangest. Sir Mark Sykes, the 6th Baronet, traveller and diplomat, wanted a room that would carry him back to one of the sultan's apartments at the Yeni Mosque in Istanbul. He commissioned an Armenian artist, David Ohannessian, whose workshop, the Societe Ottomane de Faience, produced ceramic tiles in Kutahya in Anatolia. The tiles arrived at Sledmere in 1913. Ohannessian himself would later flee the Armenian genocide and rebuild his life in Jerusalem, where his work helped define the Armenian tile tradition of the Old City. The room he made for Sykes survives on the Yorkshire Wolds, a piece of late Ottoman Anatolia tucked inside an English country house.

The Sykes family did not stop at the house. On Garton Hill, along the B1252 road that climbs the Wolds, friends and neighbours raised a 120-foot stone monument in 1865 to Sir Tatton Sykes, the 4th Baronet, who had been the local titan of his generation. His grandson Sir Mark, the 6th Baronet, raised regiments of farm boys, the Yorkshire Wagoners Reserve, from the estate at the start of the First World War. Many never came home. The Waggoners Memorial in Sledmere village, a small stone rotunda carved with battle scenes, was Mark's idea and remembers them by name. He died in the influenza pandemic of 1919, before he could see the carvings completed. The Long Library inside the house, said to have inspired the setting of M. R. James's 1924 ghost story A Neighbour's Landmark, kept reading on as if nothing had changed.