Why is the article 'the' used before Bronx?

In New York City lore, the use of the definite article “the” when describing the borough (which is also a county of New York State) derives from the colonial period, when travelers to the region where ... The borough of The Bronx is named for Bronck's River, which is named for Jonas Bronck, a settler from The Netherlands. read more

It is a left over from the original name, Borough of The Bronx (River). It is the only borough of New York City which carries the definite article ("the") in its name. read more

"They looked right smack in the middle of a map and there is the Bronx River, so they named it after the river, the borough of the Bronx, and that's why it's always called The Bronx and not just plain Bronx," Ultan says. The borough is named after the river. That's named after the man that came from a foreign land in the 17th century. read more

The Bronx is another interesting case. In 1914, 16 years after the borough was named, New York state decided to make the area into a separate county. Unsure as to why the definite article was ever included in the first place, the legislature went with Bronx County. read more