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.
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.
Although there are no surviving plans, it seems almost certain that the ornamental grounds were designed by Edward Kemp (1817-91). A report in the Dumbarton Heraldon 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.