What state was the setting for the novel "The Bridges of Madison County"?

"The Bridges of Madison County" is a 1992 best-selling novel by Robert James Waller that tells the story of a married but lonely Italian-American woman living in 1960s Madison County, Iowa. She engages in an affair with a National Geographic photographer from Bellingham, Washington, who is visiting Madison County to create a photographic essay on the covered bridges in the area. The novel is presented as a novelization of a true story, but it is in fact entirely fictional. However, the author stated in an interview that there were strong similarities between the main character and himself.

The novel is one of the bestselling books of the 20th century, with 60 million copies sold worldwide. It has also been adapted into a feature film in 1995 and a musical in 2013.

It was originally published in the UK under the title "Love in Black and White".

A sequel entitled "A Thousand Country Roads" was published in 2002. It tells the remainder of the two main characters' story after their four-day affair. They never meet again, but their lives are interlocked until death.