Common law
The common lawso named because it was "common" to all the king's courts across Englandoriginated in the practices of the courts of the English kings in the centuries following the Norman Conquest in 1066. The British Empire spread the English legal system to its historical colonies, many of which retain the common law system today. These "common law systems" are legal systems that give great precedential weight to common law, and to the style of reasoning inherited from the English legal system.
Civil law (legal system)
Louisiana private law is primarily a Napoleonic system. Louisiana is the only U.S. state partially based on French and Spanish codes and ultimately Roman law, as opposed to English common law. In Louisiana, private law was codified into the Louisiana Civil Code. Current Louisiana law has converged considerably with American law, especially in its public law, judicial system, and adoption of the Uniform Commercial Code (except for Article 2) and certain legal devices of American common law. In fact, any innovation, whether private or public, has been decidedly common law in origin. Quebec law, whose private law is also of French civil origin, has developed along the same lines, adapting in the same way as Louisiana to the public law and judicial system of Canadian common law. By contrast, Quebec private law has innovated mainly from civil sources. To a lesser extent, other states formerly part of the Spanish Empire, such as Texas and California, have also retained aspects of Spanish civil law into their legal system, for example community property. The legal system of Puerto Rico exhibits similarities to that of Louisiana: a civil code whose interpretations rely on both the civil and common law systems. Because Puerto Rico's Civil Code is based on the Spanish Civil Code of 1889, available jurisprudence has tended to rely on common law innovations due to the code's age and in many cases, obsolete nature.