During this period he appears to have become an architect. His connection to hydrography and charts fades. In 1886 he's listed in the Staten Island Directory at Richmond Road, occupation architect. He is still associated with the family firm: Charles J. Copley. In 1900 he appears for the last time in the census, his birth date 1827, place of birth England, his age 72. He lives with his brother Charles.
Today, online, searches for him bring up references [paraphrased here] to the architectural history of Roslyn Harbor Village.
William Cullen Bryant, renowned American poet and editor/half-owner of the New York Evening Post, purchased 40 acres to establish an estate in Roselyn Harbor in 1843. He later built and remodeled other houses on his estate, bringing in a variety of architectural styles and designs by well known architects and artists such as Frederick S. Copley, Frederick Law Olmstead, Clavert Vaux and Andrew Jackson Downing.
He apparently died in 1905 in Staten Island. His watercolors came to light in 2010.
Both Graham Arader and Bill Reese have looked at his work, Graham in person and Bill via the internet. Both describe him as an amateur, even a gifted amateur. Graham, who looked at each twice over an hour and a half, pronounced them good to very good. "You used to see such archives but they rarely come up anymore."
The Frederick S. Copley Wiki Bibliography.
Portraits of family and friends
History of Roslyn Harbor Village
List of known works by Charles Copley and his son Frederick