See L. M. Sears, John Slidell (1925); B. Willson, John Slidell and the Confederates in Paris (1932, repr. 1970).
Around 1910, Slidell began a period of economic and industrial growth. A large creosote plant was built, and Slidell became home to St Joe's, a major producer of bricks. A lumber mill and shipyard were also built. Following the construction of Interstate 10, Interstate 59 and Interstate 12, Slidell became a major crossroads for those traversing the Gulf States.
In 1915 the creosote plant burned to the ground killing 55 workers and 3 firefighters. The plant was rebuilt on Bayou Lane, closer to a water source and closer to a fire station. Eventually, creosote polluted the bayou which was a source of drinking water for many of Slidell's residents. The creosote plant was abandoned in 1986 and then became an EPA Superfund site. The canal was dredged and waste incinerated until completion of the cleanup in 1996. At that time a boat launch was built and Heritage Park was constructed on the former site.
With the advent of the U.S. space program in the 1960s, NASA opened the Michoud Assembly Facility in New Orleans, the John C. Stennis Space Center in nearby Bay St. Louis, Mississippi, and a NASA computer center on Gause Boulevard. This nearly tripled Slidell's population over a period of ten years, and the city became a major suburb of New Orleans. Slidell is also the location of the National Weather Service forecast office for greater New Orleans.
The city hosts several parade krewes each Carnival season. Slidell suffered extensive damage from the effects of Hurricane Katrina which hit the region on August 29, 2005. The city is said to have experienced a 23' - 26' storm surge from Lake Pontchartrain.
According to the United States Census Bureau, the city has a total area of 12.1 square miles (31.4 km²), of which, 11.8 square miles (30.5 km²) of it is land and 0.3 square miles (0.8 km²) of it (2.64%) is water.
There were 9,480 households out of which 36.0% had children under the age of 18 living with them, 57.4% were married couples living together, 14.0% had a female householder with no husband present, and 24.5% were non-families. 20.4% of all households were made up of individuals and 8.7% had someone living alone who was 65 years of age or older. The average household size was 2.67 and the average family size was 3.09.
In the city the population was spread out with 27.0% under the age of 18, 7.6% from 18 to 24, 28.5% from 25 to 44, 23.3% from 45 to 64, and 13.7% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 92.0 males. For every 100 females age 18 and over, there were 86.0 males.
The median income for a household in the city was $42,856, and the median income for a family was $48,298. Males had a median income of $40,211 versus $26,050 for females. The per capita income for the city was $19,947. About 9.5% of families and 11.8% of the population were below the poverty line, including 17.6% of those under age 18 and 7.9% of those age 65 or over.
Rather than using the airport codes of ASD and KASD for the existing Slidell Airport, or NEW and KNEW for the original New Orleans Lakefront Airport, or even MSY and KMSY for the Louis Armstrong International Airport, NWSFO Slidell uses IATA airport code "LIX" and ICAO airport code "KLIX" despite not corresponding to any actual airport.