In 1639, a Swedish captain named Jonas Bronck sailed from the Netherlands with his wife, servants, and other emigrants to New Amsterdam, which was still 25 years away from becoming ‘New York.’ Upon his arrival, the Dutch West India Company granted him about 500 acres of land that had once belonged to the Mohegan tribe. Though historical records mention Bronck paying Mohegan leaders, the details of the agreement remain unclear.
The land lay between two rivers: the Great Kill and the Aquehung (meaning 'River of High Bluffs'), which are now known as the Harlem River and the Bronx River, respectively. If the names 'Bronx' and 'Bronck' seem too similar to be a coincidence, you're not mistaken.
Bronck leased parts of his land to tobacco and corn farmers and also built a house, which is believed to have been the site of a peace treaty between the Lenape tribe and the Dutch in 1642. Unfortunately, Bronck didn’t get to enjoy his time as one of northern New Amsterdam’s hopeful settlers for long—he passed away under unknown circumstances the following year.
Although Bronck’s time in North America was brief, his connection to the area endured long after his death. His land came to be known as 'Bronck’s Land' (or 'Broncksland'), and the Aquehung was referred to as 'Bronck’s River.' While 'Bronck’s Land' didn’t stick, due to many of his tenants moving away and the influential Morris family later renaming it 'Morrisania,' 'Bronck’s River' stuck around. Eventually, it was simplified to 'Bronx River,' which later became 'the Bronx River' or simply 'the Bronx,' much like how the Mississippi River is often just called 'the Mississippi.'
In the late 1800s, New York City began absorbing the surrounding towns, ultimately merging them into the boroughs we know today. When it came to naming the borough near the Bronx, officials opted to use the name of the river that runs through it.
In other words, unlike the common practice in Southern California where people add 'the' before freeway numbers, the use of 'The Bronx' is more than just a casual habit. As for whether the 'T' in 'The Bronx' should be capitalized, that depends on who you ask. According to Bronx Borough Historian Lloyd Ultan, it should be.