Before the attack on Fort Sumter, the Southern states took several actions that could be considered treasonous or at least provocative towards the Union government. 

Some of these activities include:
Secession: The most significant action of the Southern states was their decision to leave the Union, starting with South Carolina in December 1860, followed by 10 other states. It was seen as a rebellion against the federal government and a rejection of the United States as one nation.

Formation of the Confederacy: After secession, the southern states formed their own government, the Confederacy of America, with Jefferson Davis as president. It was seen as an attempt to create a rival government and further challenge the authority of the union government. 

Confederate Property Confiscation: After several southern states seceded, Confederate troops began confiscating federal property within their borders. This included forts, arsenals and other military installations. These actions were seen as a direct challenge to the federal government and its ability to enforce its laws.

Refusal to pay federal taxes: Southern states also refused to pay federal taxes, which was seen as an opportunity to support the Union government and its efforts to keep the secession states in their hands. It was seen as a rebellion against the federal government and a rejection of its authority. All these activities, along with growing tensions between the North and South over issues such as slavery and states' rights, eventually led to the outbreak of the Civil War when Fort Sumter was attacked in April 1861.