The history of Orelans Parish and the city of New Orleans are one and the same. La Nouvelle-Orléans (New Orleans) was founded May 7, 1718, by the French Mississippi Company, under the direction of Jean-Baptiste Le Moyne de Bienville, on land inhabited by the Chitimacha. It was named for Philippe d'Orléans, Duke of Orléans, who was Regent of France at the time. His title came from the French city of Orléans. The French colony was ceded to the Spanish Empire in the Treaty of Paris (1763). During the American Revolutionary War, New Orleans was an important port to smuggle aid to the rebels, transporting military equipment and supplies up the Mississippi River. New Orleans remained under Spanish control until 1801, when it reverted to French control. Nearly all of the surviving 18th century architecture of the Vieux Carré (French Quarter) dates from this Spanish period. Napoleon sold the territory to the United States in the Louisiana Purchase in 1803. Thereafter, the city grew rapidly with influxes of Americans, French, Creoles, Irish, Germans and Africans. Major commodity crops of sugar and cotton were cultivated with slave labor on large plantations outside the city.

During the last campaign of the War of 1812, the British sent a force of 11,000 soldiers in an attempt to capture New Orleans. Despite great challenges, the young Andrew Jackson successfully cobbled together a motley crew of local militia, free blacks, US Army regulars, Kentucky riflemen, and local privateers to decisively defeat the British troops, led by Sir Edward Pakenham, in the Battle of New Orleans on January 8, 1815. The armies were unaware that the Treaty of Ghent had already ended the war on December 24, 1814.

The population of the city doubled in the 1830s and by 1840 New Orleans had become the wealthiest and third-most populous city in the nation. The Union captured New Orleans early in the American Civil War, sparing the city the destruction suffered by many other cities of the American South.

During Reconstruction New Orleans was within the Fifth Military District of the United States. Louisiana was readmitted to the Union in 1868, and its Constitution of 1868 granted universal manhood suffrage. Due to the state's large African American population, many blacks held public office. In 1872, then-lieutenant governor P.B.S. Pinchback succeeded Henry Clay Warmouth as governor of Louisiana, becoming the first non-white governor of a U.S. state, and the last African American to lead a U.S. state until Douglas Wilder's election in Virginia, 117 years later. In New Orleans, Reconstruction was marked by the horrible Mechanics Institute race riot (1866) but also by the successful operation of a fully racially-integrated public school system. Meanwhile, the city's economy struggled to right itself after practically grinding to a halt upon the declaration of war in 1861, the nationwide Panic of 1873 conspiring to severely retard economic recovery.

Reconstruction ended in Louisiana in 1877, and white southern Democrats, the so-called Redeemers, succeeded in stripping power from the Republican Party and gradually circumscribing the only recently acquired civil rights of African Americans. In New Orleans, the public schools were resegregated and remained so until 1960.

New Orleans' large community of well-educated, often French-speaking free persons of color (gens de couleur libres), who had not been enslaved prior to the Civil War, sought to fight back against the incipient forces of Jim Crow. As part of their ongoing campaign, they recruited one of their own, Homer Plessy, to test whether Louisiana's newly enacted Separate Car Act was constitutional. Plessy duly boarded a commuter train departing New Orleans for Covington, Louisiana, sat in the car reserved for whites only and was arrested. The case spawned by this incident, Plessy v. Ferguson, was heard by the U.S. Supreme Court in 1896. The court, in finding that "separate but equal" accommodations were constitutional, strengthened by effectively consecrating the already-underway Jim Crow movement. The ruling was a key development in the nadir of race relations reached during this period.

By the mid-20th century, New Orleanians were observing with concern that the city was even ceding its traditional ranking as the leading urban area in the South. By 1950, Houston, Dallas and Atlanta had surpassed New Orleans in size, and 1960 witnessed Miami's eclipse of New Orleans, even as New Orleans' population was recorded as reaching its historic peak by the 1960 Census. Like most older American cities in this period, New Orleans' center city commenced losing inhabitants, though the New Orleans metropolitan area continued expanding in population – just never as rapidly as its metropolitan peers in the Sun Belt. While the port remained one of the largest in the nation, automation and containerization resulted in significant job losses. The city's relative fall in stature meant that its former role as banker to the South was inexorably supplanted by competing companies in its now-larger peer cities. New Orleans' economy had always been more based on trade and financial services than on manufacturing, but the city's smallish manufacturing sector also shrank in the post–World War II period. Despite some economic development successes under the administrations of DeLesseps "Chep" Morrison (1946–1961) and Vic Schiro (1961–1970), metropolitan New Orleans' growth rate consistently lagged behind the more vigorous Sun Belt cities.

New Orleans was catastrophically impacted by what the University of California Berkeley's Dr. Raymond B. Seed called "the worst engineering disaster in the world since Chernobyl" when the Federal levee system failed during Hurricane Katrina in 2005. By the time the hurricane approached the city at the end of August 2005, most residents had evacuated. As the hurricane passed through the Gulf Coast region, the city's federal flood protection system failed, resulting in the worst civil engineering disaster in American history. Floodwalls and levees constructed by the United States Army Corps of Engineers failed below design specifications and 80% of the city flooded. Tens of thousands of residents who had remained in the city were rescued or otherwise made their way to shelters of last resort at the Louisiana Superdome or the New Orleans Morial Convention Center. Over 1,500 people died in Louisiana and some are still unaccounted for. Hurricane Katrina called for the first mandatory evacuation in the city's history, the second of which came 3 years later with Hurricane Gustav.

The parish has a total area of 350.2 square miles, of which 180.56 square miles is land and 169.64 square miles (48.45%) is water. The population recorded in the 1810 Federal Census was 3,190. At its peak, in 1960, the population was 627,525. The 2010 census recorded 343,829 residents in the Parish.

Neigboring parishes are St. Tammany Parish (north), St. Bernard Parish (southeast), Plaquemines Parish (southeast), and Jefferson Parish (southwest).

Birth Records - The Louisiana State office maintains records for 100 years after the date of birth. Birth records are considered confidential for the first 100 years. For current information on who may obtain a birth record as well as how to submit a request visit the Office of Public Health, Vital Records Registry website or write to them at PO Box 60630, New Orleans, LA 70160.

Birth records older than 100 years are available through the Louisiana State Archives, 3851 Essen Lane, Baton Rouge, LA 70809. (225) 922-1000.

Death Records - The Louisiana State office maintains records for 100 years after the date of death. Death records are considered confidential for the first 100 years. For current information on who may obtain a death record as well as how to submit a request visit the Office of Public Health, Vital Records Registry website or write to them at PO Box 60630, New Orleans, LA 70160.

Death records older than 100 years are available through the Louisiana State Archives, 3851 Essen Lane, Baton Rouge, LA 70809. (225) 922-1000.

Marriage Records - For current information on how to submit a request for a certified copy of an Orleans Parish marriage record less than 50 years old, see the Louisiana Office of Public Health Director, Vital Records and Statistics website or write to PO Box 60630, New Orleans, LA 70160.

Certified copies for the parish are issued by Clerk of Court. For the address of the parish Clerk of Court visit the Orleans Parish Important Addresses page.

Marriage records over 50 years are stored by the Louisiana State Archives, 3851 Essen Lane, Baton Rouge, LA 70809. (225) 922-1000.

Divorce Records - To obtain current information on how to submit a request for a certified copy of divorce records contact the Clerk of Court. For the address of the parish Clerk of Court visit the Orleans Parish Important Addresses page.