I found a family listed twice in New York City in 1870, but not in the first and second enumeration. They appeared in the second enumeration as well as their new homes outside of New York City.
This is a household located on Spring Street in New York City, 1870. First listed is Stephen Duryea, his wife Mary, and some of their children. Living in this household is also Abraham Brewer (uncle of Mary), Anna [Frances Duryea], Abraham Brewer [nephew of Abraham Brewer], and Anna Flynn.
Both groups are in New York City in 1860, but not in 1880. 1870 seems to be the time this family moved out of New York City, though not together. Stephen moved to Westchester County.
|I typed out the words for easier reading.|
Abraham moved to Rockland County and founded the Brewer Engine Fire Company in Monsey.