Surveyor and builder of roads. Born in Lady Cathcart's House in Ayr, MacAdam spent his formative years in the USA working in a counting house, and by the age of 30 he returned to Scotland wealthy. He managed a tar works at Muirkirk (East Ayrshire) and developed the process of "Macadamisation" which involves covering a road with small broken stones to form a hard surface. This led to tarmacadam (or tarmac), which greatly enhanced transport links in Scotland and is still used to cover roads today.
He died in Moffat and lies buried in the Old Churchyard there. His life is commemorated by a cairn near Muirkirk.