While today’s #stampoftheday honors a decision made in 1898, it also connects directly the inflammatory tweets about fair housing made by Donald Trump earlier this week.

The stamp itself, is a 5-cent airmail stamp, issued on July 31, 1948 to mark the 50th anniversary of the expansion of New York City – which consisted of Manhattan the Bronx—to include what had been the city of Brooklyn, as well as western Queens County, and Staten Island. The stamp itself, which was the first airmail stamp to honor something not directly connected with aviation, is oddly appealing, featuring a map of NYC as well as a golden anniversary ring encircled by seven small airplanes.

While we tend to take the city’s boundaries and its division into five boroughs as given, it’s important to recognize that those lines were the product of intense debates that have important contemporary consequences.

Let me explain. In the latter part of the 19th century leaders and residents of New York and surrounding localities – like their counterparts in many other cities – hotly debated the question of consolidation. In the end, four factors played a major role in the decision to come together.

The first factor was economic. Key civic and business leaders in New York City feared the diffuse control over the city’s harbor and waterways was undermining the city’s position as a center of American trade, particularly in light of the fact that Chicago, which was also growing and consolidating, was becoming an increasingly important economic hub. Moreover, business leaders argued, a growing number of people were working in New York City but living outside of its boundaries, in places like Brooklyn, which meant they weren’t paying for the services they consumed.

This second factor was psychological. Backers of consolidation emphasized that unless the port issues were addressed, Chicago would overtake New York (which then consisted of Manhattan and part of what is now the Bronx) and become the nation’s largest city. This prospect was intolerable for many New Yorkers.

The third factor was commercial, specifically the ways that consolidation would facilitate the development the city needed to grow. In particular, while Brooklyn had become the nation’s third largest city (in part by annexing previously independent villages) it lacked access to large quantities of potable water needed to support future growth. So real estate interests in Brooklyn, including some who also had backed construction of the Brooklyn Bridge as a way to open up the area for development, were eager to have access to the large and growing water system being developed by New York City. Moreover, the city of Brooklyn was deeply in debt, which meant it couldn’t fund other improvements needed to facilitate continued development.

Those concerned with these issues found a talented leader for their cause in Andrew Haswell Green, a lawyer, planner, civic leader, and former city comptroller who played a major role in creating many of key places and institutions that already were defining Manhattan, including Central Park, the New York Public Library, the Bronx Zoo, the American Museum of Natural History, the Metropolitan Museum of Art, Riverside Drive, and Morningside Park.

But Green could not secure the legislative support he needed until a fourth factor, politics, became part of the equation in the person of State Senator Thomas C. Platt, the longtime Republican boss of New York State. Jealous of the power and spoils won by Tammany Hall, the Democratic political machine in Manhattan had gained with support from the city’s many immigrants, Platt wanted to create a structure that would give Republicans access to those opportunities. To do so, he judged, required expanding the city’s jurisdiction so it included a majority of Republican-leaning, longer-term residents.

So in the early 1890s, with Platt’s support, the state legislature created a commission to explore consolidation, with Green at its head. He immediately proposed an ambitious consolidation plan that would be rebuffed a number of times, mostly by Brooklynites who called the movement “Green’s hobby.” Recognizing they needed some sort of popular mandate, in 1894, Green and Platt got the legislature to put a nonbinding consolidation referendum on the ballot. The campaign was heated, especially in Brooklyn where opponents of consolidation argued would allow immigrants based in Manhattan to overwhelm and destroy Brooklyn’s mostly homogenous, Protestant character. Opposition came as well from current officials who feared a loss of power as well as newspapers concerned they might lose important revenues from official advertising.

In the end, most of the surrounding municipalities voted in favor of consolidation, although Brooklyn’s pro-consolidation majority was razor thin, a scant 277 votes, 64,744 to 64,467. Green saw this as the mandate he needed. But, alarmed by the results, opponents of consolidation successfully lobbied to thwart Green’s subsequent efforts to get the state legislature to act on consolidation. However, after several more years of maneuvering, in May 1897 the state legislature passed and the governor signed legislation creating a consolidated New York as of January 1, 1898. Ironically, and contrary to Platt’s assumptions, the first person elected mayor, Robert Anderson Van Wyck, was the candidate backed by Tammany Hall.

It’s already clear that key elements of the debate – including both fear of immigrants and the ways that private actors seek and secure public-sector resources for their activities – have parallels in today’s political debates and disputes. But there’s another factor at play that relates directly to President Trump’s recent tweets attacking longstanding efforts to prevent housing discrimination, particularly in America’s suburbs.

Initially, of course, such discrimination was common and legal in cities and in suburbs. In New York City, for example publicly supported post-war efforts to create middle class housing (such as Stuyvesant Town and Peter Cooper Village in Manhattan ) initially restricted that housing to white families. Fred Trump also took advantage of the program as well as FHA loans, that also were open only to whites. But, over time, such overt discrimination became illegal. as illustrated by the fact that Fred Trump, by then in business with his son Donald, had to settle a lawsuit alleging racial discrimination brought against them by the federal government in the 1970s.

But many of those changes applied only to New York City, where the boundaries haven’t really changed since 1898. Indeed, the great wave of municipal consolidations in large East Coast cities that began in the late 1800 had pretty much played themselves out by the early 1900s. There are many reasons for this but one of the most important is the fact that local governments control land use, and, with the rise of the automobile, residents of outlying areas, particularly those with single-family homes, were wary of turning that power over to larger jurisdictions where local neighborhoods might have less power. Local control of education, particularly in light of court decisions against segregated schools, have also dampened support for further consolidation of governments in greater New York and many other urban regions.

This framework has also set the stage for decades of debates about regional equity in key areas, such as housing and education. And, it bears mention, these debates have sometimes been quite ugly. Read, for example, accounts of how in the late 1960s and early 1970s residents of Westchester County adamantly fought efforts to build affordable housing in their communities, as documented in Lizabeth Cohen’s terrific recent biography of Ed Logue. This is the backdrop for Donald Trump’s recent tweets attacking ongoing efforts to ensure that everyone has access to a variety of housing options.

This, as I’ve often tried to explain to students, is why those seemingly arcane and ancient decisions about consolidation are important today. Not only do those ancient debates turn on surprisingly contemporary themes, but also the outcomes of those debates create the framework for current decisions. And it’s why the consolidation celebrated in today’s stamp in the provides the backdrop for the president’s current efforts, which try to resurrect old tropes about suburbanites and their fears of the people who live in cities.

Be well, stay safe, fight for justice, and work for peace.