"Britain's American colonies broke with the mother country in 1776 and were recognized as the new nation of the United States of America following the Treaty of Paris in 1783. During the 19th and 20th centuries, 37 new states were added to the original 13 as the nation expanded across the North American continent and acquired a number of overseas possessions. The two most traumatic experiences in the nation's history were the Civil War (1861-65), in which a northern Union of states defeated a secessionist Confederacy of 11 southern slave states, and the Great Depression of the 1930s, an economic downturn during which about a quarter of the labor force lost its jobs. Buoyed by victories in World Wars I and II and the end of the Cold War in 1991, the US remains the world''s most powerful nation state. Since the end of World War II, the economy has achieved relatively steady growth, low unemployment and inflation, and rapid advances in technology."
The United States has a constitution-based federal government. Federalism means that the government is divided into two levels - federal (national) and state. At the federal level, the Constitution establishes three branches of government: executive, legislative and judiciary. Each of the 50 states has its own state constitution, governmental structure, courts and state-specific laws. The Constitution gives certain enumerated powers to the federal government, and those powers not vested with the federal government remain with the states.
The United States has 51 different legal systems - the federal system and one for each of the 50 states. These systems mostly fall within the common law tradition except Louisiana, which is based on Napoleonic civil code.
The federal and state legislatures are the law-making bodies of the government. At the federal level, the national legislature is called the Congress, which consists of the Senate and the House of Representatives. Members of either chamber can introduce legislation, but both houses of Congress must pass the legislation before it becomes law.
Within the executive branch, the highest office holder on the federal level is the President. The executive powers of the President include the power to approve legislation, negotiate and sign treaties, appoint federal judges, appoint cabinet and senior officers of the government, and act as the commander-in-chief of the armed forces. At the state level, governors are the chief executives.
Federal and state courts comprise the judicial branch of government. The highest court of the land is the United States Supreme Court. Each state has an equivalent state supreme court, which represents the ultimate authority on the law for that state. Federal courts have jurisdiction over federal laws and disputes that arise among states (or between citizens of different states). State courts have jurisdiction over matters pertaining to their own state laws. If there is a conflict between federal and state laws, the federal law prevails. When federal courts adjudicate cases arising under state law, the state's substantive law applies.
The following are good introductory books to the United States legal system: