boroughs have existed since the official creation of the city in 1898, when the city and each borough assumed their current boundaries. however, the boroughs have not always been part with their respective counties. before 1914, the borough of the bronx had been earlier in the southern part of westchester county which had then been annexed to new york county. before 1899, the county of queens included an eastern part, which was split off during the formation to become nassau county.