The exact date the first settlers went to the Valley of Florissant is unknown, but it is one of the oldest settlements in Missouri.

Spanish archives in Havana reveal 40 people and seven plantations were in Florissant at the time of the 1787 census.

The village, called "Fleurissant", meaning "Blooming" in English, by its French settlers and "St. Ferdinand" by its Spanish rulers, was a typical French village with its commons and common fields.

[6] Originally a separate town, and now an inner suburb of St. Louis, the community was centered on (and frequently called after) the parish of St. Ferdinand.

The center of the parish, the Old St. Ferdinand Shrine, survives and is listed on the National Register of Historic Places.

[citation needed] Around 1809, the Cold Water Cemetery had the first burial; since 2004, it has been listed in the National Register of Historic Places for its social history.

[7] As late as 1889, the town was predominantly French-speaking (while the southern portion of the metropolis was populated by German speakers).

[9] Following World War II, Florissant went from a small village community to a large suburban center, as developers such as Alfred H. Mayer Co. began building subdivisions on what was formerly farmland and empty acreage.

Around 18,000 houses were built between 1947 and 1980, and the population swelled to its peak of about 76,000 in the mid-1970s, making it the largest city in St. Louis County.

[9] James J. Eagan was the first mayor of Florissant after a charter amendment created the position.

He ultimately served 37 years from 1963 until his death on November 2, 2000, being re-elected into office nine times, and became one of the longest-serving mayors of any city in the United States.

In his final year, he was awarded the title of Best Politician in St. Louis by the Riverfront Times.

In 2012, Florissant was ranked 76 in Money magazine's top-100 list of Best Places to Live – America's Best Small Cities.

[17] The 2020 United States census[21] counted 52,533 people, 19,702 households, and 12,336 families in Florissant.

These include Atonement Lutheran School, Sacred Heart, St. Ferdinand, St. Rose Philippine Duchesne and Saint Norbert.

[30] Lindenwood University has its offsite North County Campus located in the former Our Lady of Fatima School.

Florissant is home of a number of examples of Missouri German architecture, mostly in brick commercial and institutional buildings, The finest example in the area is the Kuehn House, which has a "pronounced, toothed corbel table on its primary facade"; other notable examples are the Tebeau House and the Withington House.

[34] Examples include: Florissant is home to Northwest HealthCare, an outpatient subsidiary of Christian Hospital.

Services include: emergency department, sleep lab, bone density testing, mammography, ultrasound and MRI.

[35] A satellite facility of the Alvin J. Siteman Cancer Center that is under construction on the campus is scheduled to open in late 2019.