William Fitzjohn and his driver raced up Route 40 through Maryland, hoping to find a hot meal before the African diplomat’s meeting at the White House. It was April 1961, and segregation was the status quo in large swaths of the United States. Fitzjohn, the charge d’affaires for the country of Sierra Leone, knew that despite his elite diplomatic status, he might be turned away if he tried to eat at an establishment that discriminated against black people.

Fitzjohn had previously heard that the restaurant chain Howard Johnson’s was open to serving black customers, so his driver headed to one nearby. But when he entered Hagerstown, Maryland’s Howard Johnson’s, a surly waitress told Fitzjohn she wouldn’t serve him. Even when he showed his diplomatic credentials, she refused to budge. “It was very emotionally upsetting,” Fitzjohn told an Associated Press reporter afterward.

Fitzjohn’s experience became an international incident, prompting a presidential apology and significant publicity. But he was far from the only foreign dignitary to suffer the humiliation of segregation while in the United States. Throughout the 1950s and 1960s, African dignitaries and diplomats were repeatedly snubbed, verbally abused and discriminated against when they spent time in the U.S. Their experiences brought international attention to an uncomfortable truth: Despite promoting democracy and fighting authoritarian governments throughout the Cold War, the U.S. did not recognize or uphold the civil rights for people of color.

The disquieting reality of racial discrimination complicated the United States’ outreach to newly independent African nations. And, says historian Renee Romano, it helped pressure the government to finally throw its weight behind civil rights legislation. “It looked really bad on the world stage,” says Romano, a professor of history at Oberlin College.

As the Cold War became chillier in the 1960s, racism and discrimination became a glaring problem for President John F. Kennedy’s foreign policy. The newly elected president made energetic efforts to tout the United States as a democratic ideal for the rest of the word—efforts that were threatened by the cruelty of bias and discrimination at home.

At the time, Africa was undergoing a dramatic shift as emerging states shook off their colonial bonds. In 1960, seventeen African nations declared their independence. It was an exhilarating and precarious moment in international relations, and Kennedy had to determine his approach to the newly minted countries. He saw Africa as a potential hotbed for American-style democracy, and made an effort to welcome and host diplomats from the new nations.

But once they came to the United States along with their staffs, many African dignitaries experienced racial discrimination. Owners and employees of restaurants, barber shops, motels and other establishments in segregated states discriminated against people based on their skin color, not their diplomatic standing, and African diplomats and their staff were caught up in racist incidents.

Route 40, which connected Washington, D.C. with New York, was a particular problem for the diplomats. As they traveled from the seat of U.S. government to United Nations headquarters in Manhattan, they encountered the kind of racism that tainted everyday life for black Americans. Dignitaries were ejected from restaurants, subjected to racial slurs, refused beds in motels and turned away from private clubs patronized by members of Kennedy’s administration.

“People realized that the eyes of the world were upon us,” says Romano. “We needed to live up to some of these ideals [of democracy and civil rights] in order to maintain our international stature and uphold our ideological struggle in the Cold War.”

The incidents didn’t just cause problems for the diplomats: When news broke of yet another African dignitary being refused coffee or cursed out by a waitress, it became fodder for America’s Cold War enemies. Fitzjohn’s experience at Howard Johnson’s, for example, was decried in the Soviet Union, which upheld it as an example of American hypocrisy. The USSR even attempted to persuade the United Nations to move its headquarters out of the United States in response to the country's racist laws.

In response to a threat by African diplomats to leave the country, the U.S. State Department even created the Special Protocol Service Section, a division designed to protect African diplomats from discrimination. Its leader, Pedro Sanjuan, quickly realized that the problem wasn’t an issue of protocol—it was an issue of racism. But his attempts to expand the State Department’s attempts beyond African diplomats to help black Americans as well were largely futile.

“They started in a place of very little power,” says Romano. The group tried to persuade business owners along Route 40 to serve black patrons and real estate boards to provide housing for black diplomats and their staffs. As Sanjuan worked to try to make Route 40 more welcoming to African diplomats, he became increasingly convinced that only a legal solution could prevent business owners from discriminating against all black people.

As Freedom Riders and other protesters staged sit-ins along Route 40, the SPSS pressured state governments and Kennedy’s administration to use the law to forbid segregation. When Soviet leaders used discrimination against blacks as an example of America's double standards for democracy, it made the issue feel even more urgent. “There was an international diplomatic interest at stake,” says Romano.

Eventually, the Civil Rights Act of 1964 forbade public segregation, and the SPSS was disbanded. But the agency—and the issues faced by visiting diplomats whose skin color ensured an icy welcome to the United States—had made a difference, no matter how small.

“Mass protest and activism ultimately proved far more important in forcing reluctant legislatures to do away with discriminatory laws than pleading by the State Department,” notes Romano. But, she says, the agency did help pressure Kennedy’s government to change. The diplomats’ humiliating and scary experiences with American discrimination helped bring attention to the threats and indignities suffered by black people under segregation—a system that saw skin color to the exclusion of all other human characteristics.