Monticello is a city in and the county seat of San Juan County, Utah, United States. It is the second most populous city in San Juan County, with a population of 1,824 at the 2020 census. The Monticello area was settled in July 1887 by pioneers from the Church of Jesus Christ of Latter-day Saints. Monticello, named in honor of Thomas Jefferson's estate, became the county seat in 1895 and was incorporated as a city in 1910.