He was born in Thornhill in Dumfriesshire on 29 December 1856, the youngest son of James Williamson and his wife Margaret Wallace.[3]
He was educated at Morton School and Wallace Hall then studied Divinity at the University of Edinburgh graduating MA in 1878.[4] He was licensed to preach as a Church of Scotland minister by the Presbytery of Edinburgh in 1881.[3]
Williamson was largely responsible for co-ordinating the huge rebuilding project at St Cuthbert's by architect Hippolyte Blanc in 1892-4. This was partially funded by his predecessor Rev James Veitch. As a somewhat immodest part of the rebuilding he included a plaque to himself on the outer west face and to Rev James MacGregor the first charge minister balancing his memorial on the opposite side of the tower.[3]
He lived at 44 Palmerston Place in Edinburgh's fashionable West End.[9]
Williamson married Agnes Blackstock, the daughter of Walter Blackstock, in 1883. They had no children. Blackstock died in 1885.[15][16]
In 1888, Williamson married Elizabeth Mary Phoebe Croall,[16][17] the daughter of Robert Croall of Craigcrook Castle. They had two daughters and a son:
Agnes Honor Margaret Williamson (1889-1892), died in infancy
Robert Howard Wallace Williamson (1892-1962), buried in Warriston Cemetery
Verona Maud Williamson (1896-1980), buried in Dean Cemetery