An 1835 map of the District of Columbia, which included Georgetown and Alexandria. (Library of Congress via Wikimedia Commons)

The shape of New York City as it exists today looks nothing like it did at the town's effective founding, when the Dutch first purchased Manhattan for cheap in 1626. Over time, the city's legal boundaries would stretch to encompass what had been English-chartered towns in present-day Queens, and other remnants of New Netherland. The nearby incorporated city of Brooklyn would overrun little Williamsburg (in 1854), and eventually New York would consume them both (in 1898).

Behind every change in these boundaries — as has been true over the histories of Washington, Los Angeles, Chicago and Houston — there's a revealing story of economic interests or political fights or infrastructure change, all with implications for these places today. Modern American cities, with all their mass and influence (and their expenses and tax revenue), didn't start off that way. They annexed their way there.

This is what that history looked like in New York, from an open-data project led by Leesburg cartographer Karl Phillips, who's trying (with the help of the Sunlight Foundation and MapStory Foundation) to convert old paper maps and city records into a digital historic archive of boundary change for every city and town in America:

Across the country, here is Los Angeles:

In this way, American cities consumed outlying towns (which eventually became known as mere neighborhoods) rapidly in the 1800s, as the spread of railroads created outlying communities prime for annexation. "The prevailing wisdom at the time," Phillips says, "was that the central city should be allowed to annex any growth." New York, Chicago, Kansas City  and Boston grew this way. And as they spread, they brought the promise of infrastructure — sewer systems, electric grids, public schools — that smaller communities often lacked.

"That's one of the reasons Staten Island agreed to join New York City," Phillips says. "They were kind of a backwater part of the city, and they thought, 'If we’re annexed to New York, we’ll get all these services, the schools will improve.' "

In this way, many cities ballooned in size (while a few others, like Washington, actually shrank through secession). Detroit grew into the footprint that today feels too big for its population.

"Then you see this dramatic change in the 20th century," Phillips says. Brookline balked at joining Boston. The town of Allegheny bitterly fought Pittsburgh all the way to the Supreme Court (although it lost). At the time, in 1907, Pennsylvania required a majority of voters in both cities to opt for annexation — and, of course, the much more numerous voters of Pittsburgh prevailed. The system, Phillips says, was rigged in favor of big cities. Annexed towns were simply outvoted.

Eventually, though, railroads gave way to cars and highways, which enabled the creation of farther-flung suburbs with enough wealth to support their own infrastructure and amenities. As some cities became dirty and overcrowded, their city halls often equated with corruption, outlying towns increasingly objected. State laws were changed. "The automobile became king," Phillips says, "and the patterns changed dramatically. Now you had suburban communities fighting annexation."

Today, the borders of most big cities feel largely set (although lines within them, of neighborhoods and voting precincts, are forever fluid). But all this history remains relevant today amid the economic struggles of smaller communities looking to consolidate, and in fragmented places like St. Louis County, where it's clear that historic decisions about where to draw these lines still influence events today.

All of which is to say that Phillips's project, called the Open Boundaries Initiative, is a worthy endeavor. Folks should give him a hand.