During the time when the state capital was located in Vandalia, it was the social center of the state. The Sonnemans were one of the leading families, having settled in the area before 1850.

C.A. Sonneman was born in Gross-Reisen, Germany, February 2nd, 1813. He married Elizabeth Schmidt in 1838 and the couple soon after emigrated to the United States. They arrived in Vandalia, Illinois in 1839, engaging in commerce as a cabinet maker. When the railroad was built, Sonneman added the lumber trade to his business.

Sonneman was one of the founders and largest stockholders in the First National Bank of Vandalia. The Sonnemans were one of the charter members of the Lutheran Church in Vandalia and C.A. was a prominent Mason. At least one family member served as one of Vandalia's early mayors.

The storefront of the Sonneman's businesses is today the home of the National Road Interpretive Center of Vandalia, Illinois.