Lincoln County is a county in the U.S. state of South Dakota. As of the 2020 census, the population was 65,161, making it the third most populous county in South Dakota. Its county seat is Canton. The county was named for Abraham Lincoln, 16th President of the United States.

Lyon County is the most northwesterly county of the U.S. state of Iowa. As of the 2020 census, the population was 11,934. The county seat is Rock Rapids.