However, if this field is not meaningful, that is it is strictly for the database to internally identify a unique record, it is a surrogate key or blind key. In this case Person ID probably is an AutoNumber field, and it should not be used except internally by the database.
It's the city of New York that is divided into boroughs. In 1898, the modern city of New York was formed by merging the County of New York (modern day Manhattan and the Bronx), the then independent city of Brooklyn, Richmond County, and the western parts of then Queens County (the remainder is modern day Nassau County). To make people happy, the new city was divided into boroughs (similar to London). The original city of New York became Manhattan (named after the island it is on). The remainder of New York County became The Bronx. Brooklyn stayed Brooklyn. Queens County is also Queens. And Richmond County became Staten Island (also named after the island it is on).
West of the Bronx River (which bisects the borough) was annexed by NYC in 1874 while everything east of the river joined New York County by 1895. Until 1898, when NYC became an agglomeration of five boroughs, Manhattan and the Bronx were the same county: New York County. Finally, the Bronx became a county on its own in 1914. Today, the boroughs are coterminous as Manhattan occupies New York county, Brooklyn, Kings County, and so forth. My first two-part Westchester Square series, describing the Huntington Free Library, and Revolutionary War battle marker, seen here.