On October 2, a coalition of 15 Boston-area mayors committed publicly to facilitating the construction of 185,000 new housing units by 2030. In doing so, the mayors recognized two realities.

One, the region is dense geographically and demographically, with municipalities bleeding into one another and city limits not necessarily that well-recognized. Hence people saying they’re “from Boston” when they’re really from Quincy or Cambridge or Malden.

Second, the mayors recognized that solving something as gargantuan as the region’s housing crisis—one created by decades upon decades of poor policy and by a booming economy that continues to draw newcomers—the region’s different parts were going to have to cooperate.

This rationale behind the mayoral commitment leads to our latest open thread: To facilitate cooperation on other challenges, including mass transit, energy, and infrastructure, should Boston just go ahead and annex its smaller neighbors? Maybe everything within Route 128?

Throughout the 19th century, of course, annexations were the name of the game for Boston (much as infills were). That is how the city gained parts such as Dorchester, Jamaica Plain, Charlestown, Roxbury, and West Roxbury—independent municipalities or parts of one every last one, but now neighborhoods.

In most cases, eligible residents of the subsumed entities voted heartily to join their larger neighbor. The only exception was Brookline, which voted overwhelmingly in 1873 to remain an independent town. The last annexation was Hyde Park, which joined Boston in 1912.

That was the same year a lawmaker—from Brookline, ironically enough—proposed a plan to the state Legislature that would have had Boston annex everything within a 10-mile radius of the Massachusetts State House. That would have created a city bigger in area than Chicago or New York, and with a population now of more than two million.

For various reasons—not least prejudice against people of Irish descent then on the ascent in Boston politics—that plan went nowhere, and there was no serious consideration of further annexations until Chelsea’s financial troubles in the early 1990s.

That talk passed, too, though, and the region remains its patchwork of densely packed towns and cities, some large, some quite small; some struggling financially every year, others flush with funds—and almost all the results of borders decided decades, if not centuries ago.

Time to change it up? Absorb everything within Route 128 or so into Boston and get on with planning for an apparently booming, crowded, complicated future? Sound off in the comments below and on social.