In 1854, the Kansas Territory was organized, then in 1861 Kansas became the 34th U.S. state. In 1855, Jefferson County was established, and was named for President Thomas Jefferson. Settlement of the county was slowed by events prior to and during the Civil War, but the present day unincorporated community of Thompsonville (3 miles northwest of Perry on the Delaware River) was the first established in 1851 by Mormon settlers who initially refused to accompany the main group led by Brigham Young to the Salt Lake Valley. The settlement was first abandoned due to the violence resulting from the border wars, but was re-established when the Civil War ended.