Some neighborhood names appear to be jokes. Some have stuck around for centuries, despite changing connotations. Some shift with the winds of gentrification. Welcome to Blurred Lines, in which writer Keith Williams studies New York City's changing neighborhood boundaries.

[1868 map illustrating the 1776 Battle of Harlem Heights via Wikimedia Commons.]

Ask a handful New Yorkers to define the southern boundary of Harlem and you'll likely get a few different responses. The most popular, in my unscientific experience, is 96th Street east of Central Park and 110th Street elsewhere. A few old-timers will claim it used to dive down to 96th Street on the West Side, and other people contend that the presence of Columbia University disqualifies Morningside Heights from consideration. In recent years, development east of Central Park and north of 96th Street has caused some to question whether that area should now be considered part of the Upper East Side. I've never heard anyone, however, claim that the Harlem of today matches its original boundaries; when it was officially chartered in 1660, its southern border stretched from today's 129th Street on the Hudson to 74th Street on the East River.

The first homestead in the area we know as Harlem was established in 1639. Called Zedendaal, "Blessed Valley," it was staked by settler Jochem Pietersen Kuyter, and ran along the Harlem River from present day 127th Street to 140th Street. The native Manhattan and Lenape tribes that lived in the area would attack from time to time, and the settlers would retreat back to the safety of walled-off New Amsterdam in lower Manhattan. For a couple decades, it was rough going, with multiple wars being waged between settlers and natives, and the land was largely abandoned for a period, but by the late 1650s, the Dutch were once again keen to expand Nieuw Netherland. Peter Stuyvesant was now leading the colony, and he formally established Nieuw Haarlem, the miniature empire's second settlement in 1658.

To sweeten the deal for Nieuw Haarlem, Stuyvesant agreed to build a roadnow followed by St. Nicholas Avenuethat was eventually incorporated into the Boston Post Road. The thoroughfare allowed a number of freed Africans to join the community; in fact, the first preacher, Michael Zyperus, was an immigrant from Curaçao. He established the Reformed Low Dutch Church around 1660 on a site bound by First Avenue, East 126th Street and East 127th Street. The original location of that church would later become a "negro burial ground," and today, the church lives on as the Elmendorf Reformed Church at 171 East 121st Street.

[Harlem in 1658.]

The English took control of the area in 1664, and the new regime tried to change the name to Lancaster. It failed to stick, however, as descendants of the original settlers continued to live in the area. But the English did solidify the area's souther diagonal border, a line running west from East 74th Street near the river. It was a desirable place to live; one Dutch visitor to Haarlem in 1679 wrote of "two ridges of very high rocks, with a considerable space between them, displaying themselves very majestically." The population was centered at the confluence of five roads near today's Third Avenue and 120th Street. Two charters soon after the takeover defined the City of New York as coterminous with Manhattan Island, but the Town or Township of New Harlem appeared as a legal term well into the 1800s. (Even into the 20th century, people were contesting the division still existed.)

After a brief one-year reclamation by the Dutch in 1673, the community started to prosper under British rule. At this time, there were nearly 1,900 people living in Harlem. According to accounts, there were 75 freed Africans, 300 slaves, and about 1,500 white settlers. Several decades later, those numbers seem to have changed, as records from 1711 count 84 slaves.

By this time, the area had a relatively large population of freed Africans, and the anti-slavery movement had a stronghold in Harlem during the year's leading up to the American Revolution. Harlem became a key site for George Washington during the war, and in September 1776, the area now called Manhattanvillethen known as Hollow Waysaw some of the action in the Battle of Harlem Heights. It's an ironic name for the battle, considering the spot sits in a valley between Morningside Heights and Washington Heights (this dip is the reason the 1 train comes above ground at the 125th Street station). The Continental Army won, but the British retaliated later than year and burned Harlem down.

[Harlem's key locations in 1811.]

Rebuilding happened slowly, and in 1820, records show that there were just 91 families living in Harlem. The area was relatively inaccessible, with only two connections to New Amsterdamthe Boston Post Road or a steamboat on the East Riverbut that changed in the 1830s when service on the New York & Harlem Rail Road began, what we know as Metro-North. The train, along with the full build-out of Manhattan's street grid system, led to rapid expansion, but Harlem retained its reputation as a leisurely, country retreat for the well-to-doits name synonymous with "elegant living through a good part of the nineteenth century."

[1870 Knapp Map of Northern Manhattan via Wikimedia Commons]

Grade-level crossings went out of style by the 1870s; there were elevated lines on Second, Third, and Eighth Avenues, and what's now the Metro-North tracks were sunk south of 92nd Street. 125th Street became the center of activity in the 1880s, particularly between Park and Madison Avenues. The iconic Mount Morris Bank Building opened in 1883, the same year as the Brooklyn Bridge.

Because of new transportation options, and thanks in part to depressed property values after the Panic of 1873, East Harlem began to take on an ethnic flair. A shantytown for Italians sprung up on East 106th Street after a trolley company imported Italians to break a strike. As the elevated trains brought more immigrants to the area, "Italian Harlem" slowly expandedthis was the founding location of the Genovese crime family&3151;and until the 1920s, the area was the largest Italian population center outside of Italy. Today, there is still an enclave along Pleasant Avenue.

[Harlem's ethnic enclaves in the 1920s.]

While African Americans lived in Harlem since at least the 1650s, it wasn't until World War I when the black community began to really take root around 125th Street. Much of the immigrant labor force had returned to Europe to fight for their native flags, so industrial interests brought blacks from the South to take their placeand no doubt the presence of Jim Crow served as an impetus for many workers' moves.

The money was so good that blacks suddenly had a lot of buying power in the real estate market, and they began to take advantage of their newfound wealth. (One preacher allegedly ended all of his sermons with the advice "Buy property.") But as would be repeated countless times in the 1960s and 1970s, many white property owners did not take too kindly to this change: "The presence of one colored family in a block, no matter how well bred and orderly, was sufficient to precipitate a flight," wrote civil rights activist James Weldon Johnson in 1925. By this time, Harlem's population was nearly one-third black, and many whites resisted their new neighbors and pushed west, turning Lenox Avenue into an informal "color line."

Further north, Sugar Hill was established between 145th and 155th streets during the Harlem Renaissance of the 1920s. Because so many prominent African Americans lived here, it was known for the "sweet life," thus its name.

A Jewish stronghold had grown alongside the Italians, but was on the wane by the 1920s. In 1923, the Jewish Welfare Board predicted that "restrictions on immigration, the desire to better oneself socially as the economic status improves, [and] the influx of Negroes, Italians and Spanish-speaking groups" would lead to a shrinking Jewish population. The Jewish population in Harlem at the time was around 175,000; by 1930, it was just 5,000.

By the 1930s, enough Puerto Ricans had established roots around 110th and Lexington that the area was known as "Spanish Harlem." There was even a large shopping center under the Metro-North tracks between 111th and 116th Streets known as "La Marqueta," which has been revived today. After other ethnic groups left during the turbulent 1960s and 1970s, Spanish Harlem and East Harlem became basically interchangeable terms, along with "El Barrio."

The area known as Hamilton Heights was named after Alexander Hamilton, who lived therefrom 1802 to 1804, when he was shot by Aaron Burr in that famous duel. It had a heavy Eastern European presence from just after the Russian Revolution until the 1960s. More recently, Hispanics, particularly Dominicans, have been the majority group, although gentrification has been at work for over a decade.

As for Morningside Heights, some will find it amusing that the central campus of Columbia University used to house a facility called the Bloomingdale Insane Asylum. Bloomingdale comes from the Dutch term Bloemendaal, "valley of flowers," which was the term for much of western Manhattan north of 23rd Street; in fact, what is today called Broadway was originally known as the Bloomingdale Road. Although one public library branch still uses the term, the asylum, as you might imagine, soured the name for real estate purposes. Other names were banded about in the late 19th century, but Morningside Heights must have been the most lucrative.

[Harlem's sub-neighborhoods today.]

What's next for Harlem? The answer seems a bit rhetorical, given Columbia's expansion plans, the northward creep of the Upper East Side, and mega-developer Extell's recent strike in the heart of the neighborhood. James Weldon Johnson saw it coming; nearly a century ago, as the black population was on its way to growing nearly tenfold in just 20 years, he wrote: "When colored people do leave Harlem, their homes, their churches, their investments and their businesses, it will be because the land has become so valuable they can no longer afford to live on it."

· Blurred Lines archives [Curbed]