John Loudon McAdam lived from 21 September 1756 to 26 November 1836. A member of a minor branch of Ayrshire nobility, he made his fortune in the United States before returning to Scotland and developing an interest in road construction. He subsequently became responsible for the most important improvements in roadbuilding techniques since the Romans. The wider picture in Scotland at the time is set out in our Historical Timeline.
John Loudon McAdam was the youngest of 10 children of James McAdam and Susanna Cochrane, the niece of the 7th Earl of Dundonald. He was born in Ayr before the family moved to Lagwyne Castle. When this burned down they moved to Blairquhan Castle, also in Ayrshire. John was educated at McDoicks School of Maybole until 1770 when, at the age of 14, his father's business, the Bank of Ayr, and the family fortune both collapsed, and his father died.
McAdam, now 14 years old, was sent to live with his uncle, William McAdam, a wealthy merchant in New York. During the American Revolution between 1775 and 1783, John Loudon McAdam supported the loyalist side. He went on to make his own fortune at a very young age, becoming a successful merchant, part owner of the privateering ship "General Matthew", and a "prize agent": in effect selling goods and material captured during the war and taking a cut for doing so.
While in New York, John Loudon McAdam married Gloriana Nicoll. In 1783, he paid the price of supporting the losing side in the War of Independence, and had most of his assets seized before being put on a boat back to Scotland with his wife and two children. Back in Ayrshire, McAdam still had the means to buy an estate at Sauchrie near Maybole. Meanwhile, his close links with his relative, the 9th Earl of Dundonald, gave him a business interest in an iron works and in the production of tar-based products from coal.
John's interest in developing his estate caused him to study the way roads were constructed. At the time roads were either built, very expensively, from laid stones, or more usually were simply abysmal. His work became more widely known and in 1798, he was asked to improve the road surfaces in Falmouth. He was appointed surveyor to the Bristol Turnpike Trust in 1815, and went on to produced two papers, in 1816 and 1819, entitled Remarks on the Present System of Road-Making and Practical Essay on the Scientific Repair and Preservation of Roads. He argued that by building the road surface up above the surrounding land, by ensuring good drainage, and by using carefully graded and cambered layers of crushed stone, bound together with fine gravel or slag, roads could be made very much durable than before: and very much more cheaply. They were also cheaper and easier to maintain once built. This method represented the greatest advance in road construction since Roman times and became known as "macadamisation", or just "macadam".
By the early 1820s, some 70 turnpike trusts across the country were using McAdam as a consultant. In 1823 the UK Parliament mounted an enquiry into the state of roads across the country, which were generally perceived to be falling short of the needs of a rapidly industrialsing nation. The main outcome was the appointment of McAdam as Surveyor General of Metropolitan Roads across Great Britain. His methods subsequently became very widely used, first across Great Britain and then in America and Europe. Except for the later addition of a layer of tar to bind the road surface's stones together (a process patented by E. Purnell Hooley in 1901 as Tar Macadam or "Tarmac"), McAdam's basic techniques remain in use by road builders today. It is tempting to wonder why McAdam did not himself see the potential of using tar to bind the surface of his roads together: he had at one time, after all, owned a factory producing tar from coal. But perhaps that is simply an unfair use of hindsight.
McAdam died at the age of nearly 80 on 26 November 1836, and was buried in Moffat Cemetery.