Daniel Immerwahr teaches history at Northwestern University and is the author of “How to Hide an Empire: A History of the Greater United States.”

It’s been 17 months since Hurricanes Maria and Irma tore through Puerto Rico, but the wounds are still fresh. It took nearly a year for full power to be restored. Even now, blue tarp fills in for roofs, as Puerto Ricans await federal funding.

They have reason to wonder how much will come. According to reporting from The Washington Post, President Trump has privately insisted to John Kelly and Mick Mulvaney that not one dollar of disaster aid go to Puerto Rico. His administration has publicly opposed the extension of additional nutrition assistance funds to the island, deeming them “excessive and unnecessary.” When he speaks of Puerto Rico, Trump has a noticeable habit of addressing it in the second person. “I hate to tell you, Puerto Rico, but you’ve thrown our budget out of whack,” he scolded after Hurricane Maria.

I hate to tell you, but you’ve thrown our budget out of whack.

Puerto Rico isn’t a foreign country. It’s the United States, and its inhabitants have been citizens for more than a century. That’s because the United States extends far beyond its North American mainland. It includes the overseas territories of Puerto Rico, the U.S. Virgin Islands, the Northern Marianas, Guam and American Samoa. More than 3 million people live in those territories — more than 1 percent of the U.S. population.

Yet the true shape of the country appears to elude the present administration, which is obsessed with building a wall at the border of the contiguous United States to “protect our homeland,” as Trump puts it. When a judge in Hawaii’s U.S. District Court blocked Trump’s travel ban, then-Attorney General Jeff Sessions reported being “amazed that a judge sitting on an island in the Pacific can issue an order that stops the president.”

In neglecting the overseas parts of the country, the administration is carrying forward an attitude rooted in the long history of U.S. colonialism — a belief that some parts of the country matter and others don’t. 

This us/them distinction, which tracks closely with race, has been central to Washington’s handling of its overseas possessions for generations. Woodrow Wilson, speaking of the territories, declared in 1913 that they stood “outside the charmed circle of our own national life.” As a Supreme Court justice put it in 1901, in a notoriously convoluted phrase, they were “foreign to the United States in a domestic sense.” A part of the country, yet apart from the country. Even today, the territories can’t vote for president, can’t meaningfully vote in Congress and aren’t fully covered by the Constitution.

Historically, this exclusion has mattered tremendously. In the 1930s, it led Washington to invest little in fortifying its Pacific territories, despite the clear possibility that Japan might attack them. In December 1941, Japan did attack, striking Hawaii but also — as fewer know — the Philippines, Guam and Wake Island, all within a matter of hours. In the first draft of his Pearl Harbor address, Franklin Roosevelt planned to speak prominently of the attack on the Philippines as well as that on Hawaii, but he later crossed out that reference and focused his speech on Hawaii only. Weak defenses allowed Japan to conquer the Philippines, Guam and Wake Island in weeks. It took the western tip of Alaska, too. The U.S. military, to clear the war zone, evacuated the Aleutian Islands and interned their Native inhabitants for years.

On the mainland, this crisis slipped easily from view. Rand McNally atlases at the time listed territories that were bona fide U.S. soil as “foreign.” Few U.S. maps included the territories (as few do today). “Most people in this country, including educated people, know little or nothing about our overseas possessions,” a governmental report during the war concluded. “As a matter of fact, a lot of people do not know that we have overseas possessions.” 

Japanese occupation and the subsequent fight by the U.S. military to reclaim the territories were lethal. Manila, then the sixth-largest city in the United States, was devastated in the war. And many of the lives lost there — 100,000 is a common estimate — were claimed by friendly fire. “It was United States bombs and shells that did most of the damage,”reported the New York Times. In all, the war probably killed more than 1.5 million in the U.S. territories. More than 1 million, mostly Filipinos, were U.S. nationals. 

World War II in the Philippines was the bloodiest event ever to take place on U.S. soil, killing twice as many as the Civil War. And yet it plays little part in national memory. Even Richard Nixon, who served in the Pacific during the war, believed Pearl Harbor to be “the only piece of American territory that suffered directly from enemy attack in World War II.”

Mainland ignorance of the territories mattered during wars, but it mattered in peacetime, too. In the 1930s, a doctor named Cornelius Rhoads traveled to San Juan to study anemia. He took Puerto Rico’s subordinate status as license to practice medicine recklessly. He refused treatment to some of his patients, whom he called “experimental ‘animals.’” He tried to induce diseases in others by restricting their diets. 

Rhoads penned a letter to a Boston colleague. Puerto Ricans, he wrote, were the “dirtiest, laziest, most degenerate and thievish” people on Earth. His fellow doctors took “delight in the abuse and torture of the unfortunate subjects.” Opining that what the island needed was “something to totally exterminate the population,” he confided to his colleague that he had done his best to “further the process of extermination” by killing eight of his patients and trying to transfer cancer into others.

Rhoads’s letter was discovered before he sent it, and it became a scandal on the island. Rhoads protested that he’d been joking, and it is genuinely unclear whether he killed anyone. Nonetheless, Rhoads suffered virtually no consequences. He fled to the mainland, faced no hearings, kept his job and within a few years was elected vice president of the New York Academy of Medicine. In 1949, he made the cover of Time magazine, celebrated as a hero for his contributions to medicine.

Cornelius Rhoads, featured on this 1949 Time magazine cover, wrote in a letter to a medical colleague that he had done his best to "further the process of extermination" of Puerto Ricans by killing eight of his patients and trying to transfer cancer into others. (TIME)

The following year, nationalists led a seven-city uprising in Puerto Rico. While it was underway, two made their way to Washington to try to kill Harry Truman. They came shockingly close, and Truman named his near-assassination as a reason for declining to seek reelection. 

What motivated the assassins? One, Oscar Collazo, spoke bitterly of how Rhoads had never faced trial. The shooting, he explained, was designed to draw attention to Puerto Rico’s plight. “How little the American people know of Puerto Rico!” Collazo exclaimed. “They don’t know Puerto Rico is a possession of the United States.”

That was 1950. Yet even now, with Puerto Rico entering its 120th year as a U.S. territory, it remains obscure to mainlanders. A poll conducted after Hurricane Maria showed that only a slight majority knew Puerto Ricans were U.S. citizens and that only 37 percent of adults under 30 did. 

Puerto Rico isn’t the only territory to have courted peril in the past two years. Hurricane Irma wreaked havoc in the U.S. Virgin Islands. Last October, Typhoon Yutu became the strongest storm to hit the United States since the 1930s. It plowed into Saipan and Tinian in the Northern Marianas, though it barely made a dent in the national news. And North Korea has threatened to create an “enveloping fire” around Guam. Puerto Rico, the U.S. Virgin Islands, the Northern Marianas, Guam — those are four of the five inhabited U.S. territories. Each has faced a recent existential threat.

This will probably continue. As global warming worsens and U.S. alliances fray, the most endangered parts of the United States will be those beyond North America — and unprotected by any wall.

Trump has recently considered using funds reserved for Puerto Rican aid to pay for his border wall. Doing so would be a disaster for the millions of U.S. citizens on the island. And it would be a painful confirmation of where the “homeland” really is. 

Read more from Outlook:

Follow our updates on Facebook and Twitter