William was born in Leeds on 17 May 1828 to William Mawson, stationer and his wife Mary.
By 1851, he was living with his brother’s family in Hanover Square, Bradford and was already an established partner in the partnership with Henry Francis Lockwood of Doncaster.
He moved to Clifton Villas, never married but shared his house with various family members, including his younger brother Richard who was also an architect.
The partnership cut their teeth on less prestigious projects such as the Work House, later to become St Luke’s hospital (1852), the Bethseda Chapel and Peckover Street (1855).
However, Lockwood and Mawson were fortunate to be architects in a burgeoning and prosperous Bradford. Amongst other buildings, the partnership designed St George Hall (1853), the Wool Exchange (1867), the Town Hall (1873) and the village of Saltaire (1853), The Eye & Ear Hospital (1861), Horton Lane Congregational Chapel (1863). Their names are commemorated as street names in Saltaire. Also they designed the impressive Sion Baptist Church at the junction of Green Street and Harris Street, now a Sikh Temple and overlooking the Shipley Airedale Road.
Although much of Little Germany was designed by Milnes & France, Lockwood & Mawson designed De Vere House at the junction of Aked Street and Vicar Lane (1871).
When Lockwood died in 1878, William’s younger brother Richard became a partner.
William died on 25 April 1889.