NameMary D Looker 
Birth1804
Memo(Thomas Looker book)
Spouses
Birth1804
Memo(Rockingham Martz tree)
Death1883
Memo(Present in 1880 Census, age 75)
Marriage12 August 1831
Marr Memo(Thomas Looker book)
Parent-Proof notes for Mary D Looker
John J married Mary D (Polly) Looker 12 Aug 1831 in Rockingham County according to the Thomas Looker book. She was the daughter of John Looker Jr.
Birth, Parent-Proof, Designation notes for John J (Spouse 1)
There is general agreement in the various sources that cover the Rockingham Martz family as to the names of John’s sons. There is not as much agreement as to their order of birth, but I believe the Masanutten book is totally consistent with everything else I have learned from tombstones and Census.
I believe John J was John’s fourth oldest son. He is designated S1d.