The Missouri Constitutional Convention of 1861–1863 was a constitutional convention held in the state of Missouri during the American Civil War. The convention was elected in early 1861, and voted against secession. When open fighting broke out between Pro-Confederate governor Claiborne Fox Jackson and Union authorities, and Union forces occupied the state capital, the convention formed a provisional state government, and functioned as a quasi-legislature for several years. The convention never did produce a new constitution; that task was delegated to a new convention, elected in 1864.