Adams County is a county in the U.S. state of Iowa. As of the 2020 census, the population was 3,704, making it Iowa's least-populous county. Its county seat is Corning. Adams County was established by the state legislature in 1851 and named in honor of the second President of the United States, John Adams, or his son, the sixth President, John Qui…Adams County is a county in the U.S. state of Iowa. As of the 2020 census, the population was 3,704, making it Iowa's least-populous county. Its county seat is Corning. Adams County was established by the state legislature in 1851 and named in honor of the second President of the United States, John Adams, or his son, the sixth President, John Quincy Adams. The county was finally organized and separated from Pottawattamie County on March 12, 1853. Its original size was later reduced by the creation of Montgomery and Union counties.