Joseph Smith Jr and his brother Hyrum, were murdered by a mob of about 150 men who stormed the Carthage Jail in Carthage, Illinois on June 24, 1844.
I believe you are thinking of Joseph Smith and Hyrum Smith, leaders of the Mormon church (officially called the Church of Jesus Christ of Latter-day Saints) which was based in Nauvoo. However, they were actually killed in Carthage as they were awaiting a trial.
Joseph Smith
Joseph Smith was killed by a mob while awaiting trial in Carthage, Illinois. The trial was based on his ordering the destruction of a printing press that was causing civil disorder in Nauvoo, where he was mayor.
Nauvoo Illinois Temple was created in 2002.
Joseph Smith and his brother Hyrum were murdered while in custody at the Carthage Jail in Carthage, Illinois. Joseph and Hyrum had been charged with treason for having declared martial law and destroyed a printing press in Nauvoo, Illinois. Joseph was mayor of Nauvoo. He declared martial law and destroyed the press in an attempt to avoid a riot.The cell in which he was held was on the second floor of the jail. When the mob came up the stairs and attempted to force open the door, they shot and killed Hyrum. Joseph went to the window, looking for an escape. Another mob in the street shot up into the cell and killed him. His body fell out the window to the ground where the mob continued to shoot, stab and kick his dead body.When someone yelled: "the Mormons are coming!" The mob dispersed, and the other two inmates were spared. The bodies were conducted back to Nauvoo for burial.
The web address of the Nauvoo Historical Society is: www.nauvoohistoricalsociety.org
You are thinking of Joseph Smith, Jr. He and his brother Hyrum were shot and killed by a mob in Carthage, Illinois on June 27, 1844.
Two Hundred thousand
The address of the Nauvoo Historical Society is: 9959 Highway 195, Jasper, AL 35503
Joseph Smith Jr, the first modern prophet of the Church of Jesus Christ of Latter-day Saints (the "Mormon" church) lead his followers from New York to Ohio to Missouri to Illinois, where he was killed by an anti-Mormon mob.
1250 miles
Joseph Smith was killed by a mob while awaiting trial on spurious charges at Carthage Jail in Illinois. The armed mob of men with painted faces stormed the jail and shot him and his brother Hyrum to death.. The Wikipedia article on the subject provides a lot of detail about the subject, a link is provided.