(June 1965 image from Durham Urban Renewal Records - Durham County Library, available online at DigitalNC.org)
Based on the 1963 City Directory, the last known resident of this house was a Mrs. Ruth Williams.
By the time of the property appraisals that preceded the demolition of this house and the entire surrounding block, this and the dozen homes surrounding it had passed into the ownership of Dr. Clyde Donnell - longtime Medical Director for NC Mutual, owner of the Biltmore Hotel on Pettigrew, and chairman of the Mechanics and Farmers Bank board.
(Excerpt of appraisal of properties owned by Donnell in February 1966, sketch showing layout of homes on Mobile Avenue and Proctor Street. Durham Urban Renewal Records - Durham County Library, available online at DigitalNC.org)
Married to John Merrick's daughter Martha, Donnell was himself displaced by the destruction of Hayti when it claimed their house at 506 Fayetteville Street.
The property appraisal for 509 Mobile lists its age at 35 years, which would date construction to c.1930. This would seem to be inaccurate given that the surrounding area was developed some decades prior.