Overtoun farm is showed on General Roy's Military Survey of 1747-55 within farmland and other farming estates including Garshake, Crosslet and Barnhill. These estates combined to form part of the current designed landscape.
In 1859, Overtoun Farm was acquired by James White who had retired from the legal profession in 1851 to join his father and uncle's chemical manufacturing business which had been founded at Rutherglen in 1810.
Historical records refer to Barnhill estate as the seat of the Colquhoun family from before 1543. The descendants of the Colquhouns of Barnhill, the Campbells of Barnhill, owned Barnhill estate in the mid-19th century.
The 1st Edition Ordnance Survey map of 1860-61 shows Overtoun farmouse was connected to Barnill estate via the south approach. The Dumbartonshire Ordnance Survey Name Book of 1860 notes Barnhill is the property of Mr Campbell of Barnhill and describes the house as a good mansion with large adjoining farm offices (OS1/9/15/19). Overtoun [spelled Overton] is described as a small farm house and steading, owned by James White Esquire of Glasgow (OS1/9/15/11).
In 1836 James White of Overtoun married Fanny Campbell, daughter of Alexander Campbell of Barnhill. Their eldest son, John Campbell White (1843-1908), later became Lord Overtoun. The 1861 census records James and Fanny staying at Barnhill House as guests of her father, Alexander Campbell, likely during the construction of their new house nearby at Overtoun (Ancestry). The 1881 census return shows James and Fanny White as living at Overtown [sic] House (Ancestry). John Campbell White moved to Overtoun estate in 1891 and further expanded Overtoun House. Historic newspapers confirm that Barnhill House was used as a family residence while renovation works were undertaken to Overtoun House, further indicating the estates were under the same ownership in the mid to late-19th century (Lennox Herald, 1892).
The original land of Overtoun was confined to the east side of the Overtoun Burn, and the farmhouse of Overtoun stood on the site of the present formal garden. A tree-lined approach to the house from the south came across the park and crossed the valley to the east of the Spardie Linn by a small stone bridge. The bridge is still extant.
The 1st Edition Ordnance Survey map shows a small structure to the east of Barnhill, next to a road leading northwards from Milton. This structure was later redeveloped and became the south lodge of Overtoun House, likely around the time of the construction of the house in 1860-63. The south lodge to Overtoun House was demolished sometime after 1967. Only the gatepiers relating to this former lodge remain (LB24909). Barnhill Lodge is not shown on the 1st Edition map of 1860-61, however a newspaper rental advert from 1888 indicates the lodge was built sometime between 1860 and 1888 to service Barnhill House.
Although there are no surviving plans, it seems almost certain that the ornamental grounds at Overtoun House were designed by Edward Kemp (1817-91). A report in the Dumbarton Herald on 11 June 1863 states:
'…the grounds were laid out under the superintendence of Mr C Kemp, Birkenhead, and have been transformed from their naturally rugged condition into a state of extreme beauty.'
Although the initial is incorrect, it seems extremely unlikely that this could refer to anyone but Edward Kemp, superintendent of Birkenhead Park under the famous designer Joseph Paxton, from 1845 until his death in 1891. Paxton had previously supervised Kemp when he was in charge of the gardens at Chatsworth in Derbyshire.
Kemp practised as an independent landscape designer whilst superintendent of the park, and designed a number of public parks and private gardens throughout England. He published several works, including his General Guide in Choosing, Forming or Improving an Estate, 1850. There was a second edition entitled How to Lay Out a Garden, A General Guide in Choosing, Forming or Improving an Estate, 1858, with a further edition in 1864.
When James White died in 1884 his son, John Campbell White employed Henry Milner to design a bridge to join Overtoun with Garshake. Milner was also a landscape gardener, and his father Edward Milner had been another of Joseph Paxton's assistants. It seems certain that he would have been responsible for the planting on the west drive but who did what on other parts of the estate presents problems, given that Kemp's and Milner's dates and styles are so similar. Henry Milner's few known Scottish commissions include the enlargement of Princes Street Gardens in 1891. Like Kemp, Milner also put his thoughts on paper, in his case The Art and Practice of Landscape Gardening, 1890, which is very much based on the work of his father, Edward Milner. His father, like Kemp, had been a gardener at Chatsworth under Paxton and was then appointed to supervise a number of other Paxton projects. He was also engaged on several private commissions, the best known being Bodnant, North Wales.
Although there are no plans still in existence for the west drive, it seems obvious when one compares the layout with his writing that this is Henry Milner's design, given the fact that he was responsible for the bridge. This last phase in the layout of the estate did not occur until the death of James White in 1884. His son, John Campbell White, later Lord Overtoun, acquired the lands of Garshake on the death of his mother and was thus able to commission the building of the mile-long west approach. The last period during which the estate was managed and developed came to an end when John Campbell White died in 1908.
White had no children of his own so the estate passed to his nephew, Dr John Douglas Campbell White (1872-1940). Dr White was a GP in London and rarely came to Overtoun. Lady Overtoun continued to live at Overtoun until her death in 1931. The estate was gifted to the people of Dumbarton in 1938, thereby ridding Dr White of a costly burden.
The house was adapted as a maternity hospital and continued as such until 1970. However, many of the structures within the landscape, including the South Lodge and the Folly Castle were demolished prior to this date. Tenders were received for demolition of the walled gardens 1959-60.