William Daniel McLennan was born in Glen Street, Paisley on 12 April 1872.

He was educated first at Mr Watson's Public School in Stevenson Street, but in 1880 he was enrolled at the John Neilson Institute.

Very little is known about where he trained, but there is strong evidence that he was in the practice of William Henry  Lynn in Belfast sometime between 1890 and 1895. Lynn had previously designed Paisley Town Hall.

In 1895 he was amongst those invited to compete for Paisley Technical School and achieved some distinction by beating several leading practices to third place in Rowand Anderson's report. This encouraged him to set up practice in Paisley late in 1896 or early in 1897.

Although he registered as a probationer with the RIBA in 1891 and achieved some fame beyond Paisley in his adoption of bold and original art-nouveau variations on perpendicular Gothic and free Renaissance he never sought admission. As a person he is said to have been somewhat remote but 'clubbable' and wryly amusing with his own circle of friends. He never married and until the death of his mother in 1926 lived in the family home, Craigellan, below, in Carriagehill. 

For the last decade of his life he lived at Beltrees in Linwood (above)  in poor health and died on 6 February 1940.