Individual Details

1880 Census. Bourbon Twp, Calloway Co MO Hh 24
Joseph W. Duncan, age 38, b. MO, parents b. KY
Mary S., age 30, wfie, b. MO, parents b. KY
Sallie R., age 6, daughter. Turner R., age 6/12, b. November, son
Butler [no other name], Black, age 15, farmhand.

Mary and her brother Joel lived near each other.
1900 Census. Bourbon Twp, Calloway Co MO Hh 202
Joseph W. Duncan, b. Nov 1840, age 59, married 28 years
Mary, wife, b. Apr 1848, age 52. 2 children, both living
Hayden, son, b. Nov 1879, age 20. [looks like they changed his name...]

1910 Census. Columbia Ward 2, Boone Co, MO, Hh 218
Joseph W. "Dunkan", age 68, married one time, b. MO, parents b. KY, retired farmer
Mary S., wife, age 60, married for 37 years, 2 children, both living, b. MO, parents b. KY

FindAGrave has Turner Richard "Haden" Duncan listed ...but Haden Duncan is what is on the stone. The man was born 18 Nov 1879 - so it is obviously all the same person.

Missouri Death Certificate #24201
Mary S. Duncan of 141 Bouchelle, Columbia, widowed, died 13 Jul 1931 of a heart attack. She was born 10 Feb 1849 to Turner R. Hayden, born KY, and his wife Sallie Ann Lloyd, also born Kentucky. Mrs. Hayden Duncan of Columbia was the informant. Mary was buried Columbia Cemetery.

Birth	10 Feb 1850	Columbia, Boone County, Missouri
Marriage	15 May 1872	Joseph William Duncan
Death	13 Jul 1931	Columbia, Boone County, Missouri

Spouse	Joseph William Duncan (1842 - 1917)
Child	Sallie Redmon Duncan (1874 - )
Child	Haden Duncan (1879 - 1928)

Father	Turner Richardson Haden II (1808 - 1878)
Mother	Sarah Ann "Sally" Lloyd (1822 - 1895)
Sibling	Rebecca Edward Haden (1848 - 1940)
Sibling	Joel Thomas "Bud" Haden (1851 - 1914)
Sibling	Isaac Lloyd Haden (1854 - 1940)
Sibling	James Antony Haden (1856 - 1942)
Sibling	Margaret Haden (1858 - 1925)
Sibling	Laura Haden (1862 - 1944)
Sibling	Susan "Susie" Haden (1864 - 1949)
Sibling	Zerelda Haden (1868 - 1922)