Clinton County was formed on December 21, 1837. It was named for DeWitt Clinton, a Governor of New York, and most ardent advocate for the construction of the Erie Canal. The cities of DeWitt and Clinton were also named after him.
In 1835, Elijah Buell built a log cabin for himself and his family and was thus the first settler of the region. In 1854, the first newspaper was issued and in 1858, the Lyons Female College for girls opened its doors. The tuition was set at $175 per student.
The county has used three courthouses in its history. The structure currently in use was constructed in Romanesque style and opened in 1897.
"Clinton County was originally settled by the poorest class of people on God's earth; and it is with great pleasure that I have witnessed their progress, slow but sure and now find the most of them very comfortably situated."
2010 census recorded a population of 49,116 in the county. The current county seat is Clinton.
Clinton County cities include: Andover, Bryant, Calamus, Camanche, Charlotte, Clinton, Delmar, DeWitt, Elvira, Elwood, Goose Lake, Grand Mound, Lost Nation, Low Moor, Teeds Grove, Toronto, Welton and Wheatland.