During the period of 1821 to 1826, when St. Charles was the site of the Missouri's first State Capitol, William G. Pettus, Secretary of State for the State of Missouri, saw a need for a public market where the region's farmers and fishermen could sell their wares to the general population. In 1822 Pettus publicly requested that proposals be submitted for this project and in 1823 a two story building with a basement was built and opened as the 'Market and Fish House'. This original commercial enterprise is part of the present building that is located at 101 S. Main Street.
Much of the collection has been indexed to assist those looking for family history and genealogy. The society holds quarterly membership meetings, publishes periodicals, and sponsors various activities to promote the preservation and study of history.