NameFrances Looker 
Birth29 January 1787
Memo(Thomas Looker book, age on tombstone)
Death12 July 1844
Memo(Thomas Looker book, tombstone)
BurialMartz Cemetery, Tenth Legion, Rockingham, VA
Spouses
Birth1 May 1773, Frederick Co, MD
Memo(Thomas Looker book, find-a-grave says 30 Apr 1773)
Death1 April 1851
Memo(Thomas Looker book, find-a-grave says 7 Apr 1851)
BurialMartz Cemetery, Tenth Legion, Rockingham, VA
Marriage6 December 1803
Marr Memo(Thomas Looker book)
Parent-Proof notes for Frances Looker
Jacob married Frances Looker 6 Dec 1803 in Rockingham County according to the Thomas Looker book. She was the daughter of James Looker and granddaughter of Thomas.
Find-a-Grave notes for Frances Looker
The Rockingham Historical Society cemetery database shows Frances, consort of Jacob, died 12 Jul 1814, age 27y 5m 13d, buried at the Martz Cemetery in the Tenth Legion area. That would imply a 29 Jan 1787 date of birth.
The Thomas Looker book says she died 1 Jul 1844 age 57 years, 5 months, 13 days. And ives a date of birth of 29 Jan 1787.
Jacob consistently has a wife a little younger than himself in the 1810-1840 Census and then no wife in 1850 leading me to believe the 1844 date of death and age 57 years is accurate. This date also conforms to the idea that this couple had 13 children including several born after 1814.
And all of this is proven by her find-a-grave memorial which says she was born 29 Jan 1787 and died 12 Jul 1844.
Birth, Parent-Proof, Designation notes for Jacob (Spouse 1)
Jacob was named in his father’s will and from the order, it would seem that he was Sebastian’s fourth oldest son. However, I believe Peter was listed out of order and I believe Jacob was actually the fifth oldest.
Jacob was listed in the 1810 Census in Rockingham County, age 26-45, with three young children.
He is designated S5.
The Thomas Looker book states that “the record for Jacob Martz and his family is fairly complete, as the information came from a family Bible once belonging to Bathsheba Arts.”
Relocated and Census Tracking notes for Jacob (Spouse 1)
Jacob is present in 1810-1850 and his age in 1850 is consistent with his 1773 birth as given in the Thomas Looker book.
Death and Find-a-Grave notes for Jacob (Spouse 1)
Jacob wrote his will 16 Feb 1850 and it proved at the April Court 1851. His wife, I think, had pre-deceased hm and was not mentioned. He named son Darilas and nephew Jackson Martz as Executors. Jackson was the son of Jacob’s brother Michael.
He is listed on the Rockingham Historical Society cemetery database. They show Jacob died 11 Apr 1851 buried at the Martz Cemetery in the Tenth Legion area. The listing says age 7y 11m but I think it must be 77y 11m.
The Thomas Looker book says he died 7 Apr 1851 age 77 years 11 months and was buried at Martz Cemetery. So I don’t know if Apr 11 or Apr 7 is correct. Nor do I know how the author of the Looker book computed his birth date as 1 May 1773, you’d think she would have gone with 7 May 1773 — but no matter really.
Finally, find-a-grave says born 30 Apr 1773 and died 7 Apr 1851.