Before Lincoln took office on March 4, 1861, a provisional Confederate government was established on February 8, 1861. It was considered illegal by the United States federal government, and many Northerners thought of the Confederates as traitors. After war began in April, four slave states of the Upper South—Virginia, Arkansas, Tennessee, and North Carolina—also seceded and joined the Confederacy. The Confederacy later accepted the slave states of Missouri and Kentucky as members, although neither officially declared secession nor were they ever largely controlled by Confederate forces, despite the efforts of Confederate , which were eventually expelled. The government of the United States (the Union) rejected the claims of secession as illegitimate.