Elliott Co., Ky death records list the death on 10 Oct 1877 of Sarah J. Cox, age 58, married, born in Floyd Co., Va, parents John and Amelia Reynolds, both born in Va.

1850 census of Carter Co., Kentucky, district 1, enumerated 30 July, lists on p. 1 as family #1:
Mark Cox, 36, farmer; Sarah, 31; Jackson, 12; Ross, 10; Annes, 8; Lucinda, 7; Julia, 5; Zerelda, 2; Ballard, 8/12. Mark through Julia born in Virginia, Zerelda and Ballard in Kentucky.

1860 census of Carter Co., Ky, Bruin P.O., enumerated 22 Aug, lists on pp. 198-199 as family #1424/1308:
Martha Cox, 47 (f), farmer; Sarah J., 41; Anis, 18; Lucinda A., 16; Julia A., 14; Zerilda J., 12; James N., 9; Ben F., 4; Mark C., 2. Martha through Julia born in Virginia, Zerilda through Mark in Kentucky.

It appears likely that Mark was incorrectly entered as Martha.

1870 census of Elliott Co., Kentucky, Little Fork precinct, lists as family #37:
Cox, Mark, 57, farmer, b. Va; Jane, 51, b. Va; Vermela, 28, b. Va; Lucinda, 26, b. Va; James, 19, b. Ky; Benjamin, 14, b. Ky; Mark C., 12, b. Ky.

1880 census of Elliott Co., Kentucky, Mocassin precinct, enumerated 10 June, lists on p. 16 as family #101:
Cox, Mark, 66, farmer, widowed, Va Va Va; Ben F., 24, son, Ky Va Va; Mark C., son, 22, Ky Va Va; Sarah B., 15, granddaughter, Ky Va Va; John, 8, grandson, Ky Va Va; Sparks, Robt B., 23, works on farm, Ky Ky Ky.