Thursday night, Simone Manuel made history when she became the first black woman in the Olympics to ever earn an individual swimming gold medal and the first African-American woman to win an individual medal.

The groundbreaking win, which Manuel shared with Canada’s Penny Oleksiak after a tie, would be worth celebrating in the context of any sport. But the particularly racist history of American swimming pools — and resulting lack of opportunity for black swimmers for decades — makes it an even more poignant victory.

Phillip Merrill College of Journalism Professor and frequent ESPN commentator Kevin Blackistone said it well in the moments after Manuel got the gold:

If you know how Jim Crow metastasized in America's pools, you know how significant #SimoneManuel's gold medal is #Rio2016 #blackhistory — Kevin B. Blackistone (@ProfBlackistone) August 12, 2016

Racism is a major part of America’s swimming pool history

As Vox’s Victoria Massie wrote in June, swimming pools have always been spaces where social inequalities have played out. And as University of Montana history professor Jeff Wiltse wrote for the Washington Post last year, the nation’s swimming pool history is intimately tied to racism.

When the first public pools were established in America’s Northern cities at the turn of the 20th century, class prejudices fueled decisions of where municipal pools were built to keep out poor and working-class people, regardless of race. In the 1920s and ’30s, when pools were larger and men and women began swimming together, some major Northern cities used racial segregation tactics to prevent interactions between black men and white women.

"Southern cities typically shut down their public pools rather than allow mixed-race swimming," Wiltse said. "In the North, whites generally abandoned pools that became accessible to blacks and retreated to ones located in thoroughly white neighborhoods or established private club pools, where racial discrimination was still legal."

Physical violence and criminal charges were also common practices to keep segregation in place. In April 1950 in Pittsburgh, Nathan Albert — the secretary for the local communist club — was convicted of "inciting a riot" for allegedly trying to bring a mixed-race group to the local swimming pool two years prior.

In the 1950s, legal battles ensued. Between 1950 and 1955, the NAACP was involved in multiple anti-discrimination lawsuits for swimming pools after black patrons were denied access to swim at pools and beaches, including Isaacs v. Baltimore.

After three black children drowned in a local natural water swimming area, the NAACP brought the case and two others to the US District Court of Appeals. In light of Brown v. Board of Education, the court ruled in 1955 that segregated but equal facilities no longer sufficed. When the Supreme Court refused to hear the case, the district court’s ruling remained unchallenged, setting a new legal precedent against racist swimming pool practices.

The cause of swimming segregation: white fear of contact with black people

In a 2007 interview with NPR's Michel Martin, Wiltse, also the author of Contested Waters, a book about the history of controversy surrounding America's public pools, provided an interesting piece of insight into the anxiety around intimate contact with black people, which he said made resistance to integrating swimming pools even more contentious than integrating schools in some cases:

And so the concern among white swimmers and public officials that if blacks and whites swam together at these resort pools in which the culture was highly sexualized, that black men would assault white women with romantic advances, that they would try to make physical contact with them, and that this was unacceptable to most northern whites … … There was a court case that emerged added an attempt by the local NAACP to desegregate the municipal pools in Baltimore. And this was right after Brown v. Board of Education. And so the local attorney argued that, well, schools may be being desegregated, but we can't have swimming pools be desegregated because swimmers come in potentially intimate contact with one another. And so a federal judge upholding racial segregation of Baltimore pools reconciled his decision with the recent Brown v. Board of Education decision by claiming that pools were more sensitive than schools, and that to integrate a swimming pool would not just potentially, likely lead to race riots and all sorts of violence. And so in the interest of the public good it was reasonable to keep swimming pools segregated along racial lines, even though the Supreme Court had ruled separate but equal was unconstitutional at schools.

(You can listen to the entire interview or read the transcript at NPR.)

Of course, much of this history predates Manuel — and it’s safe to say it’s not what was on her mind as she swam to victory. But it’s all part of the story of why she’s the first black woman in her position, and why her win is being celebrated as a victory over much more than her Olympic opponents.