On 2 Dec 1860 Mercy J. first married John B. Cobb, son of John Cobb (25 Jul 1790-28 Oct 1875) & Elizabeth Bent (8 Nov 1795-11 Apr 1865), in Middleborough, MA. Born on 2 Nov 1830 in Carver, MA. John B. died in Middleborough, MA, on 19 Nov 1879; he was 49.

1865 Massachusetts Census. Middleborough, Plymouth County
John Cobb, 75, farmer
    Elizabeth Cobb, 69
    John B. Cobb, 34, shoemaker
    Marcy Cobb, 25
All were born in Massachusetts.

1870 Federal Census. Middleborough, Plymouth County, Massachusetts
Roll 639, page 481B
Post Office Wareham
    John Cobb Jr., 39, farmer
    Mercy Cobb, 30, keeping house
    John Cobb, 79, $6000 real estate
    Lizzie Briggs, 17, attending school

On 27 Nov 1881 Mercy J. second married James W. Briggs, son of Sebus Briggs (26 Sep 1795-29 Oct 1864) & Bethiah Bent (19 Feb 1797-8 Jun 1873), in Middleborough, MA. Born on 19 Jun 1826 in Middleborough, MA. James W. died in Plympton, MA, on 2 Jan 1901; he was 74.

James first married Asenath Lewis, second Mercy (Swift) Cobb, widow of John Cobb.

1900 Federal Census. Plympton, Plymouth County, Massachusetts
Roll 675, page 4B
    James Briggs, head, b. Jun 1827, 72, m. 19 years, farmer
    Mercy J. Briggs, wife, b. Feb 1840, 60, m. 19 years, no children
    Herbert E. Smith, boarder, b. Oct 1856, 43, m. 13 years, operator saw mill
    Lottie E. Smith, boarder, b. Oct 1867, 32, m. 13 years 1 child, living
    Inez E. Smith, boarder, b. Sep 1887, 12, at school
    Nancy A. Smith, boarder, b. Sep 1834, 65, widowed, 3 chirldren, 1 living
    Ira H. Stevens, board, b. Mar 1883, 17, single, day laborer
All were born in Massachusetts as were their parents.