Walter P. C. Mills in the 1850 and 1860 census
In the 1850 Census, Walter, age 9, lived in a household with his parents, Joseph and Margaret, two siblings, Eliza and Joseph, and Eliza Sammon (?), a 40 year old woman whose relationship to the family is unknown. The average household size at this time would have been 7 people.
By 1860, only Eliza and Walter are living in the household with their parents.