During the Nauvoo period of the history of The Church of Jesus Christ of Latter-day Saints, Carthage was the county seat of Hancock County, Illinois.
The county jail was located at Carthage. It was constructed of stone in 1839. It measured 29 by 35 feet, the walls being 2½ feet thick. The jail will ever be known as the site where the Prophet Joseph Smith and his brother Hyrum were killed by a mob during the afternoon of June 27, 1844. On that occasion, John Taylor was seriously wounded and Willard Richards was grazed on the ear but otherwise unhurt.
The jail was eventually sold and used for other purposes. On Nov. 5, 1903, the LDS Church purchased the jail for $4,000. The decision to do so was authorized by President Joseph F. Smith, the son of Hyrum Smith and then-president of the church.
In 1984, the LDS Church acquired the entire block on which the jail is situated. A visitors center was later constructed and dedicated in 1989 by President Gordon B. Hinckley.