Spencer is a city in the state of Iowa, United States, and the county seat of Clay County. It is located at the confluence of the Little Sioux and Ocheyedan rivers. The population was 11,233 in the 2010 census, a decline from 11,317 in 2000. Spencer has a notable Clay County Fair, held annually in September, which averages more than 300,000 visitors each year.
The town's late library cat, Dewey Readmore Books, became known throughout the world before his death in 2006. He was immortalized in the book Dewey: The Small-Town Library Cat Who Touched the World by Vicki Myron, director of the library, and Bret Witter.
When Clay County was established in 1851, it had no local government and official business was done out of Sergeant's Bluff, nearly 100 miles away on the Missouri River. In 1859, Judge Hubbard of Iowa's 4th Judicial District authorized a committee to find a site for the county seat. This committee selected "Section 20 of Spencer Township", located roughly in the center of the county near the confluence of "Sioux River and Ocheydan Creek", as the site for the "seat of justice". County Judge Charles Smeltzer approved their plan and began signing documents with the location "Spencer, Clay County, Iowa", even though he was not physically there.