An engineer and antiquarian, Clark worked for Isambard Kingdom Brunel on the Great Western Railway. In 1852 he became a trustee of the Dowlais Ironworks, effectively controlling the works until his death.

He was deeply committed to improving the appalling living conditions of the town and was Chairman of the Board of Guardians, of Merthyr Tydfil Poor Law Union, as well as the Local Board of Health.