From the Ingersoll Chronicle, Friday, November 12, 1858, pg 3, col 5: Married. On the 23rd ult., at London, by the Rev. Dr. Cooney, DD., Mr. Thomas Sear, to Miss Mary Barnum, both of Nissouri [township].
Mary was enumerated with her father's family in the 1861 census, age 21. Perhaps she was visiting there.
According to The Barnum Family, 1350-1907, 14 children were born to Mary C. Barnum and Thomas Sear/Tear.