Broadway predates any European settlements on Manhattan – it was originally a trail used by the Native Americans. The Dutch settlers turned it into a wider road from the southern tip of Manhattan (which they named New Amsterdam), up into the mainland. When the British took it over (and it later became part of the new America), it was renamed New York.
Most of the island was sparsely populated though, with only the southern end of the island fully developed. In 1811 there was a famous Commissioner’s Plan, which began development on the rest of Manhattan island, north of Houston street. This is why if you’re south of Houston, downtown New York is much more haphazard – the streets have names instead of numbers, they cross at odd angles, etc. This was the old city. North of Houston, they started with 1st street, and created the gridiron that Manhattan is famous for.
But since Broadway was already there, and since it was such a major thoroughfare, they left it as is. So it slices through the grid because it predates the grid by a few hundred years.
It’s famous for being one of the biggest streets of New York, but it’s also famous because the Theater District formed in Midtown, centered around the major thoroughfare of Broadway. New York’s biggest theaters are still called Broadway theaters to this day, and major musicals that come from New York are called Broadway shows, even though most of the major theaters aren’t technically *on* Broadway. I think there are something like 40 “Broadway theaters” in New York, most of them clustered in the theater district/Times Square area, but only 4-5 of them are on Broadway itself.
Manhattan is (mostly) on a grid system. The streets and avenues are totally straight through most of Manhattan. Streets are a standard distance apart (1/20th of a mile), and streets and avenues are of a standard width. This plan was first implemented in the 1800’s, which is after New York City was a city, and after Broadway was built. Broadway ran through most of Manhattan and was a major street so it was kept.
Broadway is famous because of theater. New York City is the musical theater capital of the USA, and arguably the world (though London’s West End might disagree with that). Most of the biggest theaters are in the Theater District, which is in Midtown Manhattan right near Broadway. If you are acting in, writing, directing, or working on a show that is on Broadway then you are at the height of the profession, it’s the theater equivalent of being in the major leagues for an athlete.
That said when talking about theater the term “Broadway” doesn’t technically refer to the street. In New York City a show can be “Broadway,” “Off-Broadway,” or “Off-Off-Broadway.” This determination is based on how big the theater is, not on the location. If a show is in a theater that seats more than 500 people that show is “on Broadway.” If the theater seats between 100 and 499 people it is “Off-Broadway.” If it seats less than 100 then it is “Off-Off-Broadway.” In fact of the 41 Broadway theaters in NYC only 4 of them are actually located on Broadway itself.
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