Post-World War II, the neighborhood underwent tremendous demographic shifts, becoming home to increasing numbers of immigrants from the Caribbean, Asia, and elsewhere.

[5] One of their primary settlements was located roughly at the current intersection of Flatbush Avenue and Kings Highway, named Keskachane or "council fire".

Midwout was established inland, in a forested area bounded by hills to the north and flat open spaces to the south,[8] which had been managed by the natives for cultivation and game purposes.

[9] The geography was created by the ancient glacier that once covered the area, leaving behind as it retreated the hills of the terminal moraine and a large outwash plain beyond.

[19] In its early years, Midwout came into conflict with its neighboring town of New Amersfoort over its borders, as well as with the local natives; in 1670 the Rockaway Indians challenged the Dutch claims, saying the Canarsee had no authority to sell the land.

By the end of the century most of the natives in the region were either dead by war or disease, or dispossessed of their ancestral lands; a few remained in Midwout as farmhands or servants for the Dutch.

The need for labor spurred the importation of African slaves, making New York one of the largest slaveholding regions in the northern English colonies.

[24] Dutch slavery was less rigid and repressive than that of the Southern Colonies, but as the English assumed control of the region, harsher legal codes came into effect.

[29] Landowners in Brooklyn were concerned that a full conflict between the Colonies and the British would result in loss of their critical source of slave labor.

[29] Some Flatbush residents maintained their loyalist sympathies: the King's Arms, for example, appeared in the town's inn for a half-century after the conclusion of the conflict.

In the second quarter of the century, a street grid was laid out, and the main north-south road was established as Flatbush Avenue.

[39] Towards the end of the century, the land was worth more if used for real estate than farming, and large landowners began selling off plots.

[43] In the face of increasing urbanization, some community leaders wished for Flatbush and the outlying Kings County towns to retain their rural character.

[44][45] Resident and amateur historian Gertrude Lefferts Vanderbilt, writing in 1881, correctly predicted a coming merger with Brooklyn, and lamented that the Dutch character of the town was gone.

The railways lived alongside five trolley lines that ran to Williamsburg in north Brooklyn and the Lower East Side in Manhattan.

[41] Development of the north end of Flatbush was helped along with the construction of Ebbets Field, home of the Brooklyn Dodgers baseball team.

[51] The response from the government was a slew of housing and tenant bills, with one allowing the city to exempt new residential construction from property taxes until 1932.

The ordinance spurred a housing boom across the borough, with significant development in the much cheaper land of southern Brooklyn and Flatbush, which was increasingly connected to the rest of the city via new infrastructure projects.

[52] Extant homes—including the neighborhood's earliest suburban development—were converted to multifamily dwellings or demolished for new homes or apartments,[41][42] which came in an array of architectural styles.

[53] Alongside the residential construction came commercial developments, from movie palaces like the Loew's Kings Theatre to department stores like Sears Roebuck & Company.

[58] By the Great Depression, Flatbush had a population of 400,000, and boasted fifteen theaters, rail and trolly lines, dozens of schools, fifty-four churches, and five newspapers.

Blockbusting encouraged white residents to sell and leave the neighborhood, and properties fell into disrepair while crime increased.

[66] Afro-Caribbean immigrants joined African Americans in moving from traditional neighborhoods like Harlem to Flatbush, particularly Haitians fleeing the dictatorial rule of François and Jean-Claude Duvalier.

[75] In the 2000s, Flatbush began to shed its poor reputation, and residents came to the area for its cheaper prices, attractive housing stock, and retail.

[76] The demographics of the neighborhood continued to shift; new Jewish residents from Syria arrived alongside Pakistanis, Bangladeshis, Russians, and Chinese.

[77] The Muslim community was hit hard in the aftermath of the September 11, 2001 terrorist attacks; an estimated 20,000 residents left voluntarily or otherwise after immigration crackdowns.

[22][55] In 1928, the Brooklyn Standard Union gave an expansive definition of Flatbush as running from Ocean Parkway in the west to Schenectady Avenue in the east, and from Prospect Park in the north as far south as Sheepshead Bay.

However they also noted that some residents still considered Midwood part of Flatbush, and the historic definitions had it stretch from Ocean Parkway to New York Avenue.

The Kings Theatre, listed on the National Register of Historic Places, operated from 1929 to 1977;[97] it reopened as a live show venue in February 2015 after extensive renovations.

[100]: 14 The concentration of fine particulate matter, the deadliest type of air pollutant, in Flatbush and Midwood is 0.0077 milligrams per cubic metre (7.7×10−9 oz/cu ft), lower than the citywide and boroughwide averages.