Here are 25 moments that create a chronology of an evolving country—and a century in which any moment might be the next big one. Many of these moments are easy to name: the assassinations, the invasions, the elections. Many are more subtle, their impact visible only in hindsight.

1. The Triangle Shirtwaist Factory Catches Fire (Mar. 25, 1911)

The Triangle Shirtwaist Company’s fire resulted in the tragic loss of nearly 150 young women and girls on March 25, 1911, in New York City. The garment workers at the company had been attempting to unionize to gain better wages and improved working conditions. The factory’s management responded by locking the workers into the building. Fabric scraps, oil and hot machines crammed into rooms on the upper floors of the ten-story building quickly unleashed an inferno within the building. With the exits blocked, girls attempted to use the rusted fire escape or jump from windows into the fire department’s dry-rotted nets, only to plunge onto the pavement in front of bystanders below. The tragedy was exasperated by the failure of the U.S. government to protect its citizens who were working in deplorable conditions, but it was difficult for anyone who saw the corpses lined up on sidewalks waiting for identification to deny the need for labor reform and improved fire safety equipment. The deaths unified female labor reformers of the Progressive era.

Triangle Shirtwaist Factory Fire, 1911. (New York Public Library / Getty Images)

2. The Great Migration Begins (1915)

In today’s world African Americans are viewed as urban people, but that’s a very new phenomenon: The vast majority of time that African Americans have been on this continent, they’ve been primarily Southern and rural. That changed with the Great Migration, a mass relocation of 6 million African Americans from the Jim Crow South to the North and West, starting in 1915.

This leaderless revolution, a response to oppression in the South, was set in motion by the labor shortage in the North during World War I. And once the door opened, a flood of people came. Those who migrated became the advance guard of the Civil Rights movement; they shaped our culture, from music to sports. On the other hand, one of the responses to their presence was fear and hostility. In these big cities that they had hoped would be refuges, they were still blocked from the American dream. The Great Migration was a watershed demographic change in our country’s history—and we’re still living with its effects today.

African American men, women, and children who participated in the Great Migration to the north, with suitcases and luggage placed in front, Chicago, 1918. (Chicago History Museum / Getty Images)

3. The Prophet Is Published (Sept. 23, 1923)

In the aftermath of World War I, the Lebanese-born, Boston-based poet-philosopher Kahlil Gibran wrote what would become one of the world’s most translated works of philosophy: The Prophet. This collection of inspirational sermons delivered by a fictional prophet—on love, marriage, work, reason, self-knowledge and ethics—challenged tired orthodoxies and oppressive ideologies. Though Gibran’s exaltation of human individuality, creativity and difference was not entirely original, the book’s success lay in his ability to make his insights feel like revelations. Ever since its publication in 1923, The Prophet has been a salve for readers who tried—in good American fashion—to break from conformity. Gibran readers include Woodrow Wilson and American soldiers during World War II (thanks to its selection for the American Services Editions in 1943); Elvis Presley and Johnny Cash; members of the 1960s counterculture and now Salma Hayek. The Prophet taught self-trust amid the buzzing, blooming confusion of modern America. Sometimes it takes a foreigner to speak the voice of Americans’ inner conscience.

Kahlil Gibran in 1897. (Royal Photographic Society / Getty Images)

4. The KKK Marches in Washington (Aug. 8, 1925)

When the KKK paraded down Pennsylvania Avenue in Washington, D.C., the headline in the New York Times declared “Sight Astonishes Capital: Robed, but Unmasked Hosts in White Move Along Avenue.” The marchers, the article noted, received “a warm reception.” The parade took place in broad daylight, in the nation’s capital, and most of the participants were from the north. This event symbolizes the Nadir of Race Relations, a terrible era from 1890 to about 1940, when race relations grew worse and worse. During this period white Americans became more racist than at any other point in our history, even during slavery. Also during the Nadir, the phenomenon of sundown towns swept the North. These are towns that were for decades—and in some cases still are—all-white on purpose.

Among the other terrible legacies of that period are its inaccurate white supremacist histories of everything from Christopher Columbus and U.S. Grant to Woodrow Wilson, and the astounding gap between black and white media family wealth— problems that we are still trying to transcend.

Members of the American white supremecist movement, the Ku Klux Klan, marching down Pennsylvania Avenue in Washington, D.C., in 1925. (Topical Press Agency / Getty Images)

5. Thomas Dorsey Invents the Gospel Blues (1932)

In Chicago in 1932, an African American composer named Thomas A. Dorsey, who had been a nightclub jazz pianist, wrote a song inspired by his wife’s death in childbirth. The song, “Take My Hand, Precious Lord,” unexpectedly became the foundation for the modern African American gospel music tradition. Its success stimulated an entirely new music industry—the gospel blues. It became a touchstone for the dramatic role that music played in sustaining and forwarding America’s Civil Rights movement; Martin Luther King Jr. often asked supporters to sing it before they marched, including the night before his assassination. The gospel blues also brought singers such as Mahalia Jackson, Sister Rosetta Tharp, and the Golden Gate Quartet to prominence and was later foundational for Aretha Franklin and Whitney Houston, among many others. That tiny, inauspicious moment in 1932 created a subtle yet profound change in American life, ultimately producing musical anthems of powerful personal, moral, and political transformation.

Thomas Dorsey, pictured circa 1970. (Michael Ochs Archives / Getty Images)

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