On this day 100 years ago, a White mob unleashed the deadliest Election Day violence in US history

A historical marker was unveiled on June 21, 2019, in Orlando, Florida, nearly 100 years after July Perry was lynched by a white mob after a friend tried to vote.

(CNN)It's been 100 years since the Ocoee Massacre, a dark and often overlooked chapter in American history.

On November 2, 1920, African American residents of Ocoee, Florida, went out to cast their ballots in the presidential election -- no small task at the time.
In the decades since Reconstruction, Florida politics had been dominated by White Southern Democrats, who fought to preserve slavery in the 1850s and had since obstructed African Americans from exercising their constitutional rights through violence, intimidation and legislation.
But in the run-up to the 1920 election, Black people in Ocoee were registering to vote in droves -- a reality that threatened the grip of white supremacy, wrote Paul Ortiz, a history professor at the University of Florida, in a 2010 essay.
    "State and local officials -- along with the Ku Klux Klan -- understood that white supremacy was in trouble," Ortiz wrote. "They responded mercilessly."
    In an attempt to prevent Black people from voting, a White mob in Ocoee killed dozens of African Americans, set fire to their houses and drove them out of the community.
    It was "the single bloodiest day in modern American political history," Ortiz wrote.

    It stemmed from one Black man's attempt to vote

    It's hard to detail exactly how the events of that day, known as the Ocoee Massacre, transpired. Records that do exist are few and far between and contradictory -- experts say that's because local officials succeeded in their attempts to cover up what happened.
    But in recent years, historians have pieced together oral histories, land records and published accounts to put together a more accurate version of events and ensure that the massacre isn't forgotten -- an effort documented in a recent report by the Orlando Sentinel.
    According to several histories of the massacre, it started when Moses Norman, a prominent Black landowner in the Ocoee community, turned up to the polls and attempted to cast his ballot.
    Norman was turned away by poll workers who told him that he hadn't properly registered or paid the poll tax, according to a 2014 article in the Florida Historical Quarterly. So he took the issue to a prominent Orlando lawyer and Republican Senate candidate, who advised that Norman return and demand he be allowed to exercise his right to vote.
    Norman returned, with some reports indicating that he had a gun with him as he went up to the poll workers and others saying that White people found the gun in his car. Ultimately, he was again driven away by White residents and went to take refuge at the house of his friend July Perry, another prominent Black man in the community.
    A White mob formed and set out to find Norman, eventually arriving at Perry's home, where a group of African American residents had assembled. It's unclear who fired first, but violence broke out, leaving two White men dead and Perry injured, the authors of the Florida Historical Quarterly article wrote.
    After the initial gunfight, the mob called in reinforcements and came back with a vengeance.
      More than 250 White people, among them members of the Ku Klux Klan, torched rows of houses where African Americans lived, and set fire to other community buildings. Perry was lynched in Orlando. It's not clear how many African Americans were killed, though estimates range from about 30 to as many as 50.
      Despite their efforts to fight back, nearly all of the African Americans in Ocoee were driven out of town and didn't return to live there for decades.