For 400 years Carbeth (‘castle of the birches’) was held by a branch of the Buchanan family. Thomas Buchanan acquired the lands of Carbeth in 1476, and his son was the first Buchanan of Carbeth. There are suggestions that building foundations remain from the time of acquisition. However, the earliest established date for the older, eastern part of the building comes from a marriage stone, dated 1716, discovered above a fireplace on the third floor.
It is known that by 1840 the eastern part of the building existed in its current castellated form. This work was completed for John Buchanan. He inherited Carbeth from his father, also John, who died in 1825. John Buchanan married Mary Louisa Bayley in 1835; they had five daughters, three of whom died young. John Buchanan made improvements to the estate, including building the stables and improving the Home Farm. He also donated the land and contributed to the costs of building the Free Church in the village (now the pharmacy).
One year after his death in 1872, his two surviving daughters sold Carbeth. Their mother and one daughter, Ann Jane, who was not married at that point, built Dunkyan, in the village, to live in. Mrs Buchanan died in 1880. Ann Jane continued to live there until her death in 1928, the last Buchanan of Carbeth (in 1894 she married Archibald Bell).
There was a direct link from the third Buchanan of Carbeth to the 15th President of the USA, James Buchanan. He was President 1857–61, but failed to stop the American Civil War which broke out shortly after he left office.
Carbeth was bought by a Mr Forester, who then had to sell it again in 1879 as a result of the failure of the Glasgow Bank. It was bought by David Wilson, a Glasgow cotton merchant. He built the rather more extravagantly designed western part of the house shortly after he had purchased the estate. His son, also David, continued to improve farming practice and was very active in promoting new scientific methods in agriculture. He also served as the county councillor for Killearn for 41 years. He was knighted in 1920 for services to agriculture.
His oldest son, David, was killed in the First World War. His second son, John, was wounded in the war. He managed the estate and was Keeper of the Royal Philatelic Collection from 1936 to 1969. George, his third son, was also an enthusiastic farmer and agricultural improver. He continued his father’s commitment to the area by becoming county councillor after his father stood down. Between them they served on the council from 1889 to 1975. He also played a major part in the work of the Killearn Trust as a founder trustee from 1932 and as Chairman from 1971 to his death in 1979. He was knighted for his services to agriculture in 1959.
In 1972, the first edition of the Parish of Killearn book noted that Sir John had brought the house up to date ‘without in any way detracting from his grandfather’s conception of a thoroughly comfortable and well-appointed family dwelling house, and must rank as one of the best examples of a mansion of the 1880s’. Sir John died in 1975. In the early 1980s, Carbeth was sold and converted into nine apartments.