Just after noon on Sept. 16, 1920, a wagon filled with window counterweights exploded in the heart of Wall Street, killing 38 people and injuring over a hundred more. The blast gouged a 2-foot-deep crater where the wagon had been parked; to this day, nearby walls are pockmarked from where the pieces of metal dug into the masonry.

A mail carrier collecting letters found unusual warnings stuffed into a mailbox shortly before the bomb went off.

In case there was any doubt about the likely culprits, the letters pointed a direct finger: Anarchists. This was an era in which the relatively new philosophy of communism intermingled with anarchism, the fight for organized unions and -- particularly in New York -- a massive influx of immigration. A militant strain of anarchism espoused by an Italian immigrant named Luigi Galleani apparently inspired his followers to target the Morgan bank on Wall Street after Galleani was deported, part of a national crackdown on immigrants following World War I.

That same year, the nation was preparing to elect a new president. Woodrow Wilson wasn't nominated for a third term, with his Democratic party turning to Ohio Gov. James Cox as its presidential nominee and nominating as vice president a distant cousin of former president Teddy Roosevelt named Franklin. On the Republican side, Ohio senator Warren Harding earned the nomination.

Shortly after the Wall Street bombing, Harding gave a speech in his home state railing against "hyphenated citizenship" -- which can be summarized fairly simply as an immigrant's dual embrace of his native country and his adopted one, the United States. It's a variation on the complaint that Gov. Bobby Jindal offered during his brief stint on the campaign trail in 2015. "I don't know about you," he said in April of last year, "I'm tired of the hyphenated Americans. No more 'African-Americans.' No more 'Indian-Americans.' No more 'Asian-Americans.'"

Harding was more vague.

"Let us all pray that America shall never become divided into classes and shall never feel the menace of hyphenated citizenship," he said. He continued: "For Americans who love America, I sound a warning. It is not beyond possibility that the day might come -- and may God forbid it -- when an organized hyphenated vote in American politics might have the balance of voting power to elect our government." If that happened, he warned -- if immigrants who identified with countries other than the United States were elected to office -- control of the nation "might be transferred to a foreign capital abroad."

For the the editorial board of The Washington Post, that was a call to action. As the Center for Global Development's Michael Clemens noted on Twitter on Tuesday, The Post published a virulent editorial against immigrants — titled "Americanism Aroused" — in the wake of Harding's warning and the Wall Street attack.

"Senator Harding's warning against the danger of a hyphenated citizenship emphasizes at the psychological moment a question which is neither sectional nor political, a danger which goes to the root of all problems confronting this country today," the editorial began. "The eradication of foreignism is the outstanding task which America must confront in the next decade."

The authors go on to suggest that the New York bombing "emphasizes the extent to which the alien scum from the cesspools and sewers of the Old World has polluted the clear spring of American democracy." The editorial rails against Wilson's League of Nations and calls for passage of the "Johnson bill" -- a reference to immigration legislation that would eventually evolve into the Johnson-Reed Act of 1924.

Legislation curtailing immigration had been passed by Congress prior to the Wall Street bombing, but President Wilson vetoed the measure. The 1920 election changed things.

Harding's opponent, Cox, was hardly progressive by modern standards; on the front page of the Sacramento Union newspaper the day Harding's hyphen remarks were covered, this editorial cartoon depicting Cox appeared.

(Note the writing on the piece of paper.)

That November, Cox won only the states of the old Confederacy, swapping Kentucky for Tennessee. Shortly after his inauguration in 1921, Harding called Congress into special session to pass new limits on immigration, which he then signed into law. The 1924 Johnson-Reed Act -- which became law under Calvin Coolidge after Harding's death in office -- imposed new restrictions on Asian immigration and focused on preserving American homogeneity. (The 1920 Census, incidentally, offered seven options for race: white, black, mulatto, Chinese, Japanese, American Indian and other.)

Warren Harding is today remembered for the series of scandals that plagued his administration. As one more sign that history repeats itself, Harding at one point reportedly came to blows with an administrator who he felt had betrayed him. That bureaucrat was Charles Forbes, who ran the Veterans Bureau.