So many decisions have gone into the development of Boston and its neighborhoods during the last 200 years that it’s hard to pick the most consequential. Here are five candidates.

What other big decisions have there been? And which ones do you wish could be reversed?

The decision: To fill in the back bay.

Boston was no stranger to reclamation by the time the state, the city, and various landowners reached an agreement in the late 1850s to begin filling in the brackish tidal basin colloquially known as the back bay.

During the first two decades of the 19th century, Beacon Hill’s original summit had been used to fill in a pond that became the Haymarket Square area. Various other smaller parts of the once-hilly, unmistakably peninsular city had been reclaimed in similar ways throughout the early 1800s.

But the more than 600-acre infill of what became the Back Bay neighborhood was truly epic for the time. No U.S. municipality had attempted a reclamation project on that scale. The decision to do so had its skeptics, and the project seemed to take forever (sound familiar?).

Commenced in 1857 with gravel from Needham, the infill was not finished until 1882.

The net effect: A vastly expanded Boston, including the new neighborhood, which developers, government entities, and private organizations would pepper with posh homes and major institutions.

The decision: To not incorporate surrounding towns and cities into Boston.

In January 1912, Daniel Kiley, a state legislator from Brookline, proposed a bill that would have incorporated into Boston every town and city within 10 miles of the Massachusetts State House, thereby creating a municipality bigger in area than New York, Chicago, and Philadelphia.

That would have meant 32 locales, from Wakefield through Quincy and Waltham out past Winthrop, becoming neighborhoods within the City of Boston. It would have left behind a 327-square-mile city of around 2,000,000 residents today.

The idea was not so far-fetched. On New Year’s Day 1912, Boston officially incorporated Hyde Park as what turned out to be its southernmost neighborhood. And the city had gone on a veritable incorporation spree throughout the 1800s (never mind the massive infill project that spawned Back Bay). Plus, a union of various towns, cities, and counties had birthed modern New York City in 1898.

Alas, Kiley’s legislation went nowhere. For whatever reasons, Boston’s big-city features, including its large number of Irish immigrants, spooked enough leaders and residents in the ‘burbs to have them decide nay instead of yay.

The net effect: The present-day shape, give or take some infill, of modern-day Boston as well as a Boston that, while it punches well above its weight among major U.S. cities, is still relatively small in both population and area; and a condemnation of residents of Cambridge, Somerville, et al, to having to decide whether to just say “Boston” when people outside of New England ask where they’re from or risk being more specific.

The decision: To raze the West End.

Starting in the late 1950s, Boston officials oversaw the wholesale demolition of several acres of the West End and the displacement of thousands of residents, many of them long-timers. The photo above is from February 1960.

It was all in the name of urban renewal, a mid-20th-century effort that turned out to be far from renewing for many neighborhoods in several cities nationwide (check out Robert Caro’s The Power Broker for the gory details).

Developers, with official encouragement, plonked high-rises in place of the West End’s more intimate streets and lower-rise dwellings; and that was that: a neighborhood undone and cut off from the vibrancy of the rest of Boston.

Today, it would be difficult to find anyone who thinks the city’s decision to raze most of the West End was a good idea. There was an official apology (of sorts) in September 2015, with a promise that the city would be more surgical in subsequent such efforts.

The net effect: The decimation of an entire area of downtown Boston and the benchmark against which other large-scale redevelopments of Boston are measured.

The decision: To build what turned out to be Boston’s tallest buildings in a line that became known as the High Spine.

In the very early 1960s, an 11-member group of architects calling themselves the Committee on Civic Design sought to save Boston from the idea that the powers that be were then batting around, which was: Build high-rises throughout Back Bay and other low-rise areas of the city.

The solution the committee came up with? Build skyscrapers along a ribbon from Huntington Avenue to where Back Bay meets the South End. The Pru would wrap construction in 1964—with more construction quickly following that decade, as pictured above—and work along the ribbon continues to this day.

The net effect: That High Spine concept, preserving the character of various areas of the city while also remaking the skyline.

The decision: To sink the Central Artery (a.k.a. I-93) through Boston.

Of all the huge decisions that have altered Boston’s physical makeup, the decision by all levels of government to sink the Central Artery and thereby loose what came to be known as the Big Dig is, well, probably the biggest. Or at least the biggest for most Bostonians today, the one terrain-altering project everyone over 25 can kvetch about (and praise).

MassDOT has called the Big Dig ”the largest, most complex, and technologically challenging highway project in the history of the United States.” Just a couple of statistics to appreciate the scope of the project’s construction: It involved excavating 16 million cubic yards of dirt, enough to fill a stadium to the rim 16 times; and workers poured 3.8 million cubic yards of concrete, enough to build a sidewalk 3 feet wide and 4 inches thick from Boston to San Francisco and back three times.

What did it accomplish? The Big Dig expanded I-93 and, more importantly, put its Boston portion underground; extended I-90 to Logan Airport via the Ted Williams Tunnel; added two bridges over the Charles, including the Zakim; and spawned 300 acres of open space, including the Rose Kennedy Greenway.

Like with the Back Bay infill 130 years before, it also seemed to take forever: The Big Dig largely wrapped in 2006, after 15 years of continuous work (the above photo’s from 1994).

The net effect: A much better-connected Boston.

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[Sources not already cited: William Marchione, The Charles: A River Transformed, pages 45-8; Chris Marstall, “Welcome to Mega-Boston,” The Boston Globe, January 22, 2012]