Some Cassidys I found in 1855:
1st ED Ward 5 of Kings County City of Brooklyn
Family 378 House 84 Frame $800
Margaret Cassidy, 56 yrs old, F, wid, Born Ireland, living 2 years in the
City, Alien, cant read or write
Francis Cassidy, 14years old, m, w, son, Born Ireland, living 2 years in
the City, Alien, book binder
Patrick Cassidy, 18 years old, son, m, w, Born Irealnd, living 2 years in
the City, Alien, Book binder
Family 520 House 123 Frame $3,000
Margaret Cassidy, 33 years old, f, married, 1 year in the city, Alien,
own's house
Richard Cassidy, 10 years old, m, son, born Ireland, 1 year in the city, Alien
Ellen Cassidy, 12, f, born Ireland, 2 year in the city, Alien
Constantine Cassidy, 8, m, born Ireland, 1 year in the city, Alien
Catherine Cassidy, 6, daughter, f, born Ireland, 1 year in the city, Alien
Mary Cassidy, 4, Daughter, f, born Ireland, 1 year in the city, Alien
Margaret Cassidy, 1, f, daughter, born Ireland, 1 year in the city, Alien
2nd ED Ward 5 House 14 Family 36
Julia Cassidy, 60, f, born Orange County, wid, 15 years in the city
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Cassidy, McAree, McGee, Marran, Byrnes, Pattison [Patterson], Cox
Abbott, O'Brien, Rourke, Freemont, Collins
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Cassidy, McAree, McGee, Marran, Byrnes, Pattison [Patterson], Cox
Abbott, O'Brien, Rourke, Freemont, Collins