In 1656 Sir George, Viscount Tarbat, Lord MacLeod and Castlehaven (1632-1714), created Earl of Cromartie (1703), bought the lands of Milton from Sir Walter Innes of Inverbreakie (Invergordon). At this time Sir George's seat was the Tarbat peninsula, 20km to the north-east, comparatively remote from Milton which lay within easy reach of Dingwall, Cromarty, Tain and the safe, navigable waters of the Cromarty Firth. He renamed this property, 'New Tarbat', and developed a new house beside Milntown Castle, a tower house built by the Munros in the 16th century. This was to form the new centre of his northern estates, providing a suitable location for developing the ports and shipping essential for the success of Tarbat estate's grain trade.
New Tarbat House seems to have been designed by Lord Tarbat himself. The building and furnishing of New Tarbat was a major project from the 1650s until the 1710s, alongside the building of Royston House, his Edinburgh mansion. Several gardeners were employed from the 1680s onwards, notably William Frogg (d.1718), and extensive formal gardens were laid out with parterres set below a formal terrace to the south, overlooking the Cromarty Firth. The main approach to the mansion was diagonally from the west, along a double avenue, the northernmost arm of a patte d'oie. On meeting the main axis the avenue widened out into a broad grass ride, on an axis with the House and lined by a single avenue of trees (May, 1755). The entrance court before the house was set with lead statues including one of Cain and Abel, and another of Neptune sent up 'north in John Morison's ship 4th October 1712' (Clough, 1990, p.83). Also in the consignment was 'A Large box with the head of THE IRON GATE...Two garding SPADES' and a 'water ingan' (engine, or fountain) first conceived in 1706. It is described in an order placed with the sculptor Ibrach (Rysbrach?), London in 1711. The ornate fountain was:
'according to Sir John Mayor's pattern as good in all respects as that was when first made of brass and iron and led to force water thirty or forty feet high through a pipe two inches boore and more if required, and also three figures, one a man and two wimmen wone with a (moon?) and the other a swan standing by them and the man with the sunn at his feet al three five foot high and more and also twenty yeards of lead pipes 2 inches boore at two pence the pound, the three figures and Ingen coming to twenty-five pounds…'.
In the event the fountain was never erected and lay in boxes, being noted subsequently in various inventories (Clough, 1990, pp.92-8).
To the south of the mansion was a stone terrace with a central flight of steps leading down to a Long Walk oriented east-west. This allowed views out southwards over a parterre, with compartments laid out probably in scrollwork. To either side lay a wilderness of bosquets with cross-paths and to the east of the mansion was an enclosed court, with a long lawn set with a mount (site of Milntown Castle?) beyond.
Between 1714–25 John, Master of Tarbat, 2nd Earl of Cromartie (c 1658-1731) spent his time in Edinburgh and London. By the time George MacKenzie, 3rd Earl of Cromartie (1704-61) came into possession of New Tarbat on his coming of age and marriage in 1725, the farmland was run down and New Tarbat was suffering from lack of investment. He refurbished and repaired the house, harled the exterior and improved the grounds. He directed the mason Alexander Stronach to build gatepiers and erect the iron gate sent from Royston in 1712 (see above). Land improvements were carried out at New Tarbat and Castle Leod (see Castle Leod).
When the Tarbat Estates were forfeited between 1746-84, the house was neglected while the gardens gradually fell into ruin, although the gardener and a team of men were kept on between 1749-53. In 1760 the Factor of the Annexed Estates of Lovat and Cromartie considered the acquisition of timber at New Tarbat for smelting. An account of the standing timber in the policies details that the parkland and gardens were planted with ash, elm, lime and white poplar. There was a preponderance of alder, whin and sycamore including a number of:
'young forest trees in and about the garden of New Tarbat which may be cut down without hurting the Policy'. There is mention of vandalism in the gardens where 'some time ago some wicked fellowes have cutt off a part of the lead of one of the statues at New Tarbat, in the night time, and have disfigured one of them very much. It is a statue of Cain and Abel who stood before the entry of the house and it is a pity that such insolence should pass unpunished…some time ago there was an Arm cutt from another of the statues of which no discovery was made.' (Clough, 1990, pp.96-7).
The house deteriorated, Thomas Pennant's account in 1774 mentioning 'the swallows flying in and out and making their nests in the fine plasterwork of a once-great mansion'. The house was thereafter used as a girnel, for a short time as a spinning factory and eventually Captain John Mackenzie of Avoch became tenant of the Home Farm with his living quarters in part of the mansion. By 1784, when John MacKenzie, Lord MacLeod (d.1789) regained his estates, New Tarbat was ruinous and it was demolished. He commissioned James McLeran to design a new classical mansion house, Tarbat House, said to incorporate some of the remains of New Tarbat house. Retaining the avenues, he embarked on a replanting programme, which was unfinished on his death in 1789.
There were few developments at Tarbat until the estate was inherited by Ann Hay MacKenzie (1829-88), in 1849. Her marriage with George Granville Sutherland-Leveson-Gower, Marquis of Stafford, later to become 3rd Duke and 21st Earl of Sutherland, brought investment into the Tarbat Estates. On Countess Ann's death in 1888, the estate passed to Francis (her second surviving son), who was succeeded five years later by Sibell Lilian MacKenzie, the last member of the family to reside at Tarbat. Sibell married Colonel Edward Walter Blunt-MacKenzie and the family lived at Tarbat, Castle Leod and Kildary House. When widowed, she took up permanent residence at Tarbat. On her death in 1962, the estate was sold, changing hands several times between 1962 and the present. In 1987, Tarbat House was the subject of arson and left in a semi-ruined condition. The house remains in private ownership.