Mary Ann Spencer Stowe Fassett was born about 1825 in Ohio. She first married ? Stowe and had Robert W. Stowe abt. 1846. I do not know what happened to Stowe. She moved with her parents, Willis and Nancy (Ayers) Spencer, to Wisconsin abt. 1848 and was listed in the 1850 census with them. She had a sister named Eunice Samantha and a brother named George B. George's wife was named Clara. Other siblings were Electa and Rhodana.
She married Lucius Fassett before 1853. She and Lucius had William b.abt.1853, Nancy A., b.abt. 1855, Clarissa, Lucius, and George B. Lucius married a Martha after Mary Ann died.
My brother and his wife have my Spencer materials now, but when I can get access to them again, I would be glad to share what I have. I would love to have more information about your line.