I would look in Alabama for marriage. A Nancy J Williams listed on 1860 census, and Nancy J Davis and JF Davis on 1870 census Dale Co, AL
Name: Nancy J Williams
Age: 10
Birth Year: abt 1850
Gender: Female
Birth Place: Alabama
Home in 1860: Dale, Alabama
Post Office: Newton
Dwelling Number: 1467
Family Number: 1467
Attended School: Yes
Household Members:
Name Age
J W Williams 31
Elizabeth A Williams 29
Sarah A Williams 13
Nancy J Williams 10
Sephronia E Williams 7
James E Williams 4
Daniel D Williams 1
in the 1870 United States Federal Census
Name: Nancy J Davis
Age in 1870: 19
Birth Year: abt 1851
Birthplace: Alabama
Dwelling Number: 19
Home in 1870: Beat 12, Dale, Alabama
Race: White
Gender: Female
Post Office: Barnes Cross Roads
Occupation: Keeping House
Inferred Spouse: J F Davis
Inferred Children: Wm E Davis
Household Members:
Name Age
J F Davis 19
Nancy J Davis 19
Wm E Davis 1/12