On August 8, 1925, more than 50,000 members of the Ku Klux Klan paraded through Washington, D.C. Some walked in lines as wide as 20 abreast, while others created formations of the letter K or a Christian cross. A few rode on horseback. Many held American flags. Men and women alike, the marchers carried banners emblazoned with the names of their home states or local chapters, and their procession lasted for more than three hours down a Pennsylvania Avenue lined with spectators. National leaders of the organization were resplendent in colorful satin robes and the rank and file wore white, their regalia adorned with a circular red patch containing a cross with a drop of blood at its center.

Nearly all of the marchers wore pointed hoods, but their faces were clearly visible. In part, that was because officials would sanction the parade only if participants agreed to walk unmasked. But a mask was not really necessary, as most members of the Klan saw little reason to hide their faces. After all, there were millions of them in the United States.

Most Americans today likely think of the Ku Klux Klan as an organization whose heyday came in the civil-rights era of the 1950s and 1960s, and of its members as lower-class white Southern men—ones who concealed their identities while waving the Confederate flag at pro-segregation rallies, burning crosses on the lawns of their enemies, or brutalizing their innocent victims. Others are perhaps familiar with the Klan of the 1860s and 1870s, which was a white and distinctively Southern terrorist organization composed of men who tortured and murdered people under cover of darkness in an effort to undermine the political and economic freedoms accorded to formerly enslaved people during Reconstruction.

But the Klan was easily at its most popular in the United States during the 1920s, when its reach was nationwide, its members disproportionately middle class, and many of its very visible public activities geared toward festivities, pageants, and social gatherings. In some ways, it was this superficially innocuous Klan that was the most insidious of them all. Packaging its noxious ideology as traditional small-town values and wholesome fun, the Klan of the 1920s encouraged native-born white Americans to believe that bigotry, intimidation, harassment, and extralegal violence were all perfectly compatible with, if not central to, patriotic respectability.

The Ku Klux Klan had been defunct for nearly a half-century when William J. Simmons decided to revive the organization in the fall of 1915. A resident of Atlanta, Simmons worked for a fraternal benefit society called the Woodmen of the World, and he already belonged to more than a dozen clubs and churches. But he had dreamed for years about founding a fraternal order himself someday, and with D.W. Griffith’s cinematic paean to the Klan, The Birth of a Nation, scheduled to debut in Atlanta, the inspiration and the timing seemed right. On Thanksgiving night, after riding with about 15 other men in a rented tour bus to a large granite formation outside of the city known as Stone Mountain, Simmons lit a wooden cross aflame and announced the rebirth of the Knights of the Ku Klux Klan.

Advertised by Simmons in Atlanta newspapers as “The World’s Greatest Secret, Social, Patriotic, Fraternal, Beneficiary Order” and a “High Class Order for Men of Intelligence and Character,” the new Klan floundered for several years. It had attracted just a few thousand members by the spring of 1920, when Simmons hired Mary Elizabeth Tyler and Edward Young Clarke as publicity agents and promoters for the group. Tyler and Clarke divided the entire country into what amounted to sales territories and they sent more than 1,000 solicitors into the field to recruit members whose $10 membership fee for the Klan went in part to the solicitors as commission.

Tyler and Clarke’s strategies were immensely successful, swelling the national membership of the Klan to over 100,000 within a matter of months. In 1921, a newspaper exposé detailed more than 100 acts of Klan-sponsored vigilante violence and prompted a congressional investigation, but the ensuing publicity only made the Klan stronger. It claimed more than 1 million members by early 1922. Internal squabbles and power struggles led to the ouster of Simmons from his leadership post later that year, and he was replaced by a dentist from Texas named Hiram Evans. Organizational infighting and external opposition notwithstanding, the Klan continued to grow. By 1925, it had anywhere from 2 million to 5 million members and the sympathy or support of millions more.

The Klan drew historical inspiration from the Reconstruction-era Southern past and had its headquarters in the South, but white Americans flocked to the organization all across the United States. Klan chapters could be found in cities, towns, and rural areas alike, and the organization had strongholds not only in former Confederate states like Arkansas, Georgia, Alabama, and Texas, but also in Indiana, Oregon, Kansas, Colorado, Pennsylvania, Washington, and Ohio. Typical members were neither wealthy and powerful nor impoverished and dispossessed. Rather, they were middle-class white American men and their families: small-business owners and salesmen, ministers and professors, clerks and farmers, doctors and lawyers.

Ideologically, the Klan blended xenophobia, religious prejudice, and white supremacy together with a broadly conservative moralism. Amidst a global recession that came in the aftermath of World War I, fear and anxiety were widespread among native-born white Protestants that the country they had known and been accustomed to dominating was coming undone. They worried about an influx of eastern European immigrants who adhered to Communism and other supposedly subversive political creeds, about the seemingly growing influence of Catholics and Jews in American life, and about the migration of African Americans out of the South. The intellectual vogue for religious modernism, the expansion of political and sexual freedoms for women, and the perception that immorality, crime, and vice were all on the rise only confirmed the sense that the world was spinning beyond their control.

The Klan advocated the restoration of “true Americanism” and offered members a platform that demonized blacks, Catholics, Jews, Mexicans, Asians, and any other non-white ethnic immigrants while also condemning Communism, most other forms of leftist politics, and “base” cultural influences such as alcohol, birth control, and the teaching of evolution in public schools. Presenting itself in part as a Christian moral reform organization and in part as a vehicle for entrenching the economic and political power of white Anglo-Saxon Protestants, the Klan flourished with the promise that energetic white nationalism and traditional morals would hold back the tides of modernity and ensure that forces scheming to undermine the authority of native-born white Americans would be kept at bay.

Unsurprisingly, such an antagonistic worldview produced and sanctioned a great deal of violence. From the late 1910s through the 1920s, Klansmen carried out hundreds of beatings and whippings, and dozens of murders. They threatened bootleggers, flogged Mexicans, tarred and feathered doctors who performed abortions, and strong-armed politicians. They lynched black people, showed up on night rides to terrify prostitutes, bullied Jews, and lashed young women found riding in cars with men.

But the violence was not the attraction for most members of the Klan. Indeed, most would likely have disavowed their support for such activities, and many surely did not consider themselves to be mean-spirited racists at all. The Klan owed its popularity less to its endorsement of raw hatred directed toward non-whites and the supposedly immoral than to how it allowed for the expression of white supremacy and moral conservatism in culturally acceptable and even ostensibly laudatory ways.

Like many organizations that presented themselves as fraternal orders, the Klan gave members the sense that they belonged to something special, complete with secret rituals; handshakes; mystical-sounding titles, like Imperial Wizard and Exalted Cyclops; code words; and uniforms. The Klan sponsored parades and picnics, baseball teams and beautiful-baby contests. Klansmen had musical troupes that performed public concerts and bands that played at state fairs. It had extensive women’s auxiliaries and even a number of auxiliaries for children, which had names such as the Junior Ku Klux Klan, the Tri-K Klub, and the Ku Klux Kiddies.

Klan members showed up in churches on Sunday mornings to donate money and they ran charity drives. They threw Christmas parties for orphans and raised money to build Protestant-only hospitals. They made efforts to fight supposed Catholic influence in public schools by donating American flags and Bibles. They created special Klan rites for wedding ceremonies, christenings, and funerals. They ran candidates for hundreds of state and local offices, and Americans elected countless Klan members as mayors, school-board and city-council members, sheriffs, and state legislators. Klan officeholders in particularly prominent and powerful positions included Governors Edward Jackson of Indiana and Clifford Walker of Georgia, as well as U.S. Senators Earle Mayfield of Texas and Rice Means of Colorado.

For every Klansmen who joined for the opportunity to bully, threaten, and beat blacks, immigrants, and adulterers, there were dozens attracted by these sorts of avenues for communal and civic engagement, for forging business and political connections to other middle-class white people, and for the chance to be publicly proud of being white, Protestant, and a native-born American.

None of which is to suggest that the ideology of intolerance or the racist violence was separable from the forging of community, the charity work, the pride, or the political activism. On the contrary, it was all of a piece, and even Klan members who came to the organization mostly because friends and neighbors encouraged them to do so saw the appeal of white supremacy and understood full well how the appearance of Klansmen in regalia struck fear into large numbers of their fellow Americans.

One factor that helped bring down the Klan was a growing recognition that that fear was legitimate. Presidents Warren Harding and Calvin Coolidge both opposed the Klan, and as the years went on a growing number of public officials and prominent citizens who had joined the Klan as its numbers increased in the early 1920s turned against the organization as it became clear that they had cast their lot less with a salutary fraternal society than with a conspiracy that countenanced sadists and fanatics.

Ultimately, the march in Washington, D.C., in the summer of 1925 would prove to be the symbolic high point of the 1920s Ku Klux Klan. By the end of the decade, its numbers had dwindled practically into insignificance. But it would be a mistake to think that a backlash against the Klan’s violence was the central cause of its demise. The United States was fortunate to have presidents during the 1920s who saw the Klan for the public menace that it was, but the Klan did not disintegrate because of the fundamental liberality of white Americans and the nation’s leaders. Rather, it went into decline mostly because of its own self-destructiveness, the fierceness and constancy of its opponents, and changing socioeconomic and political contexts that deprived the Klan of much of the energy that had given it life.

Klan leaders notoriously oversaw local and state chapters as dictators and stole funds from organizational treasuries, and the stream of members who left in frustration became a flood by the end of 1925 after the conviction of David Stephenson, the leading Klansmen in Indiana, for murdering a young woman he had also brutally raped. That scandal was shocking to Klan members who valued the group’s alleged commitment to moral integrity, but it was no surprise to the many Protestant ministers, black civil-rights organizations, newspaper editors, and Jewish and Catholic groups who had been vocal and courageous in their opposition to the Klan from the very beginning.

Perhaps most important in bringing down the Klan was that the vision of an America decaying from foreign ideologies, dangerous immigrants, and moral rot never came into being. The post-World War I recession eased and by the middle of the 1920s the American economy boomed again. Labor disputes that Klansmen warned came from Communist agitation faded, black migration proceeded without causing massive unrest and social revolution, immigration restrictions passed in 1924 limited the number of people arriving from eastern Europe, and the age of the flapper moved ahead whether moralists liked it or not.

Amidst it all, white native-born Protestants still retained the lion’s share of the power in the United States, and they did not need the Klan to hold it. Even without the Klan, the nation remained a place where prejudice against ethnic and religious minorities was widespread and where black Americans in particular suffered legalized discrimination and deadly violence.

Still, there was something especially disturbing about a United States in which bigotry’s appeal had become so public and widespread that it could be taken for granted, and where its purveyors could feel entirely comfortable expressing it through such seemingly virtuous activities. In a country that normalized the Ku Klux Klan, it hardly mattered whether every white American felt the organization’s allure. Sizable percentages of them probably wanted nothing to do directly with the Klan at all. But if they were not interested in watching the parade go by, they mostly just looked the other way.