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. Each state's constitution differs from one another. This is because each state has its unique history, needs, philosophy, 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 clarified 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
Since 1860, dual federalism continued, but the power of the federal government began to strengthen. The Great Depression in the 1930s brought the end of dual federalism. States were unable to cope with the economic upheaval. Instead, President Roosevelt's "New Deal" brought about a system of "cooperative federalism". Instead of assigning specific functions to each level of goverrnment, Roosevelt encouraged the national, state, and local governments to work together on specific programs.