State governments have their own constitutions, similar to that of the national Constitution; however, the laws made in individual states cannot conflict with the national Constitution. The state constitutions all differ because each state has unique histories, needs, philosophies, and geography.
During the first 100 years of United States history, the states did most of the governing that directly affected the people. The national government mainly concentrated on foreign affairs. This is known as "dual federalism," where each level of government controlled its own sphere. However, during this time a rift began to form between the two over the issue of who had sovereignty that would culminate in the Civil War.
This issue was resolved following the Civil War. After the war, a series of constitutional amendments were passed that spelled out the federal government's control over social and economic policy and protection of the civil rights of citizens.
The Civil War Amendments