On June 14, 1920, the John Robinson Circus arrived in Duluth Minnesota for a free parade and a one-night performance. Two local white teenagers, Irene Tusken, age 19, and James "Jimmie" Sullivan, 18, met at the circus and ended up behind the big top, watching the black workers dismantle the tent, load wagons and generally get the circus ready to move on. 

Later that night Sullivan claimed to his father that he and Tusken were assaulted, and that Tusken was raped and robbed by five or six black circus workers, who were part of the crew.  

In the early morning of June 15, Duluth police chief John Murphy received a call from James Sullivan's father, saying six black circus workers had held his son and girlfriend at gunpoint and then raped and robbed Irene Tusken. Chief Murphy lined up all 150 or so roustabouts, food service workers, and props-men on the side of the tracks and asked Sullivan and Tusken to identify their attackers. The police arrested six black men as suspects in connection with the rape and robbery and held them in custody in the city jail.  

Sullivan's claim that Tusken was raped has been questioned. When she was examined by her physician, Dr. David Graham, on the morning of June 15, he found no physical evidence of rape or assault.  

Newspapers printed articles about the alleged rape; rumors spread in the white community about it, including that Tusken was dying from her injuries. That evening, a mob of between 1,000 and 10,000 men formed outside the Duluth City jail.

The Duluth commissioner of public safety, William F. Murnian, ordered the police not to use their guns to protect the BLACK prisoners. 

The mob used heavy timbers, bricks, and rails to break down doors and windows, pulling the six black men from their cells. The mob seized Elias Clayton, Elmer Jackson, and Isaac McGhie. They took them out and convicted them of Tusken's rape in a kangaroo court. The mob took the three men one block to the intersection 1st Street and 2nd Avenue East, where they beat them and hanged them from a light pole.  

The June 15 Ely Miner reported that just across the bay in Superior, Wisconsin, the acting chief of police declared: "We are going to run all idle negroes out of Superior and they're going to stay out." How many were forced out is not certain. All of the blacks employed by a carnival in Superior were fired and told to leave the city.  

Two days later, on June 17, Judge William Cant and the grand jury had a difficult time identifying the lead mob members. In the end the grand jury issued thirty-seven indictments for the lynching mob. Twenty-five were for rioting and twelve for the crime of murder in the first degree. Some men were indicted on both charges. Three men: Louis Dondino, Carl Hammerberg, and Gilbert Stephenson were convicted of rioting; none served more than 15 months in prison.

No one was prosecuted for the murders of the three black men.  

Details obtained from: https://en.wikipedia.org/wiki/Duluth_lynchings