Unfortunately, I was unable to find any information about a "Chickasaw Agency" point of interest in Illinois. However, there is a Chickasaw National Recreation Area located in Sulphur, Oklahoma.

The Chickasaw National Recreation Area is a stunning landscape of natural springs, streams, and lakes. Visitors to the park can enjoy hiking, fishing, camping, and picnicking. The park is also home to a variety of wildlife, including deer, foxes, and over 200 species of birds.

One of the unique attractions of the Chickasaw National Recreation Area is the Travertine Nature Center, which offers interactive exhibits and educational programs about the park's geology, ecology, and cultural history. The park also features historic structures, including the Chickasaw Cultural Center and the Vendome Well, which was once a popular destination for those seeking the healing properties of the area's mineral waters.

Overall, the Chickasaw National Recreation Area is a beautiful and fascinating destination for anyone interested in the natural world, history, or outdoor recreation.