The first European explorers to visit Louisiana came in 1528. The Spanish expedition (led by Panfilo de Narváez) located the mouth of the Mississippi River. In 1541, Hernando de Soto's expedition crossed the region. Then Spanish interest in Louisiana lay dormant. In the late 17th century, French expeditions, which included sovereign, religious and commercial aims, established a foothold on the Mississippi River and Gulf Coast. With its first settlements, France lay claim to a vast region of North America and set out to establish a commercial empire and French nation stretching from the Gulf of Mexico to Canada.

The French explorer Robert Cavelier de La Salle named the region Louisiana to honor France's King Louis XIV in 1682. The first permanent settlement, Fort Maurepas (at what is now Ocean Springs, Mississippi, near Biloxi), was founded by Pierre Le Moyne d'Iberville, a French military officer from Canada, in 1699.

The French colony of Louisiana originally claimed all the land on both sides of the Mississippi River and north to French territory in Canada. The following States were part of Louisiana: Louisiana, Mississippi, Arkansas, Oklahoma, Missouri, Kansas, Nebraska, Iowa, Illinois, Indiana, Michigan, Wisconsin, Minnesota, North Dakota, South Dakota.

The settlement of Natchitoches (along the Red River in present-day northwest Louisiana) was established in 1714 by Louis Juchereau de St. Denis, making it the oldest permanent settlement in the Louisiana Purchase territory. The French settlement had two purposes: to establish trade with the Spanish in Texas, and to deter Spanish advances into Louisiana. Also, the northern terminus of the Old San Antonio Road (sometimes called El Camino Real, or Kings Highway) was at Natchitoches. The settlement soon became a flourishing river port and crossroads, giving rise to vast cotton kingdoms along the river. Over time, planters developed large plantations and built fine homes in a growing town, a pattern repeated in New Orleans and other places.

Louisiana's French settlements contributed to further exploration and outposts, concentrated along the banks of the Mississippi and its major tributaries, from Louisiana to as far north as the region called the Illinois Country, around Peoria, Illinois and present-day St. Louis, Missouri. See also: French colonization of the Americas.

Initially Mobile, Alabama and Biloxi, Mississippi functioned as the capital of the colony; recognizing the importance of the Mississippi River to trade and military interests, France made New Orleans the seat of civilian and military authority in 1722. From then until the Louisiana Purchase made the region part of the United States on December 20, 1803, France and Spain would trade control of the region's colonial empire.

Most of the territory to the east of the Mississippi was lost to the Kingdom of Great Britain in the French and Indian War, except for the area around New Orleans and the parishes around Lake Pontchartrain. The rest of Louisiana became a colony of Spain after the Seven Years' War by the Treaty of Paris of 1763.

During the period of Spanish rule, several thousand French-speaking refugees from the region of Acadia made their way to Louisiana following British expulsion; settling largely in the southwestern Louisiana, the Acadian refugees were welcomed by the Spanish, and descendants came to be called Cajuns.

In 1800, France's Napoleon Bonaparte acquired Louisiana from Spain in the Treaty of San Ildefonso, an arrangement kept secret for some two years.

Then in 1803, Bonaparte sold the territory to the United States, which (see Louisiana Purchase) divided it into two territories: the Orleans Territory (which became the state of Louisiana in 1812) and the District of Louisiana (which consisted of all the land not included in Orleans Territory). The Florida Parishes were annexed from the short-lived and strategically important West Florida Republic by proclamation of President James Madison in 1810.

The western boundary of Louisiana with Spanish Texas remained in dispute until the Adams-Onís Treaty in 1819, with the Sabine Free State serving as a neutral buffer zone as well as a haven for criminals. Also called "No Man's Land," this part of central and southwestern Louisiana was settled in part by a mixed-race people known as Redbones, whose origins are the subject of ongoing debate.

Louisiana was a slave state. It also had one of the largest free black populations in the United States.(see slavery) In the American Civil War, Louisiana seceded from the Union on January 26, 1861. New Orleans was captured by Federal troops on April 25, 1862. Because a large part of the population had Union sympathies (or compatible commercial interests), the Federal government took the unusual step of designating the areas of Louisiana under federal control as a state within the Union, with its own elected representatives to the U.S. Congress.

Further information: Effect of Hurricane Katrina on Louisiana and Effect of Hurricane Katrina on New Orleans. On August 29, 2005, Hurricane Katrina struck and devastated southeastern Louisiana, while damaged levees in New Orleans flooded the city. The city was essentially closed until October. Estimates are that more than two million people in the Gulf region were displaced by the hurricane, with more than a thousand storm fatalities in Louisiana. Public outcry criticized the government at the local, state, and federal levels, citing that response was neither fast nor adequate. The next month, southwestern Louisiana was struck by Hurricane Rita.

The current Louisiana governor is Kathleen Babineaux Blanco (Democrat), and its two U.S. senators are Mary Landrieu (Democrat) and David Vitter (Republican). Louisiana has seven Members of Congress: five Republicans and two Democrats.

The Louisiana political and legal structure has held over several elements from the time of French governance. The first is the use of the term "parish" in place of "county" for an administrative subdivision. The second is the legal system. Louisiana is the only American state whose legal system is based on civil law, which is based on French and Spanish codes and ultimately Roman law, as opposed to English common law, which is based on precedent and custom. Louisiana thus follows the system of most non-Anglophone countries in the world. It is incorrect to equate the Louisiana Civil Code with the Napoleonic Code: although the Napoleonic Code strongly influenced Louisiana law, it was never in force in Louisiana, as it was enacted in 1804, after the Louisiana Purchase of 1803. While the Louisiana Civil Code of 1870 has been continuously revised and updated since its enactment, it is still considered the controlling authority in the state.

Great differences still exist between Louisianian civil law and the common law found in the other U.S. states. While some of these differences have been bridged due to the strong influence of common law in the United States, it is important to note that the "civilian" tradition is still deeply rooted in most aspects of Louisiana private law. Thus property, contractual, business entities structure, much of civil procedure, and family law are still mostly based on traditional Roman legal thinking. In contrast, criminal law is entirely based on the Anglo-American common law.

Louisiana is unique among U.S. states in its method for state, local, and congressional elections. All candidates, regardless of party affiliation, run in an open primary on Election Day. If no candidate has more than 50% of the vote, the two candidates with the highest vote total compete in a runoff election approximately one month later. This runoff does not take into account party identification; therefore, it is not uncommon for a Democrat to be in a runoff with a fellow Democrat or a Republican to be in a runoff with a fellow Republican. All other states use single-party primaries followed by a general election between party candidates, each conducted by either a plurality voting system or runoff voting, to elect Senators, Representatives, and statewide officials.

The state's principal agricultural outputs include seafood (It is the biggest producer of crawfish in the world), cotton, soybeans, cattle, sugarcane, poultry and eggs, dairy products, and rice. Its industrial outputs include chemical products, petroleum and coal products, food processing, transportation equipment, paper products, and tourism.

Louisiana has 3 personal income tax brackets, ranging from 2% to 6%. The sales tax rate is 1%: a .97% Louisiana sales tax and a .03% Louisiana Tourism Promotion District sales tax. Political subdivisions also levy their own sales tax in addition to the state fees. The state also has a use tax, which includes 4% to be distributed by the Department of Revenue to local governments. Property taxes are assessed and collected at the local level.