I've found the last of the known daughters of Dennis and Catherine Casey Cussen/Cushing.
Johanna was born in Galbally in 1836, travelling with her family to Newfoundland, Boston, and Fort Winnebago by about 1848. In about 1858 she married George O'Connell, I believe a recent immigrant from New Brunswick, Canada, and they settled in Lodi, about 25 miles south of Fort Winnebago. They were farmers. From 1860 to 1876 they had thirteen children in Lodi: Katie (1860), Ellen (1861-1931), John F (1863), Mary E. (1864-1937), George, Jr. (1865), Joanna (1866, m. Edward Kerrigan), James E. (1868), Maggie (1869, m. John Bastian 1906), Frances (1871, died 1873), William (1873, died at 6 weeks old), Daniel (1874, died in 1888), Alice (1875), and Mark (1876). George, Sr. died in 1877, leaving Joanna with 11 children between the ages of 4 and 17 and a farm to run. I have no records over the next 20 years, so don't know how she managed. By 1900, Johanna was living in Portage, near Fort Winnebago, with only James remaining at home. She remained in Portage until her death, in 1923, and is buried with her family in St. Patrick's Cemetery in Lodi.
A side note: In 1860, 27 year old Michael Welch, also from New Brunswick, was living with George and Johanna. Ten years later he married Johanna's younger sister, Ellen Cushing. A brief google indicates that Michael's mother's name may have been O'Connell, so he and George may have been cousins.
Another side note: As I research Johanna's family, I find that their last name is O'Connell only on the markers of their Lodi graves. George O'Connell's marker looks to be an original tombstone, strong evidence of the last name O'Connell. Nonetheless, every other record I've found, for generations, gives a last name of Connell and I've decided to use this as the family name.