The Second Spanish Period began in Florida, lasting from 1784 to 1821. The Treaty of Versailles, part of the Treaty of Paris of 1783, gave British residents of Florida 18 months to relocate.

Father Thomas Hassett conducted a census of St. Augustine in 1786. This census accounts for the city's population, around 2,000 inhabitants at the time.

On June 8, 1789, James Madison introduced his proposed amendments to the Constitution, later known as the Bill of Rights.

In 1786, the Spanish crown ordered the construction of a new parish church for St. Augustine.

In 1795 Spain receded to France all of the land west of the Perdido River, in what was known then as West Florida.

In 1796 Spain and France signed the Treaty of San Ildefonso (Separate from the Treaty signed in 1800). This treaty allied the two nations against English and American intrusions.

On October 1, 1800 Louis A Berthier representing France and Don Mariano Luis de Urquijo for Spain signed the Third Treaty of San Ildefonso.

Georges Biassou (1741-1801) arrived in St. Augustine in 1796 with thirty loyal Haitian followers.

Robert Livingston, James Monroe, and Barbe Marbois negotiated the Louisiana Purchase, signed on April 30, 1803 in Paris. Jefferson announced the treaty to the American people on July 4.

In 1808 the residents of St. Augustine erected the pillars of the City Gates using coquina blocks. The Cubo Line was also reconstructed at the same time.

In 1810, the people of West Florida met at Baton Rouge and declared themselves independent.

The United States Congress passed a secret authorization for President Madison to seize East Florida.

The Patriot War, from 1812 to 1814, was fought between residents and troops of Spanish Florida and "Patriots" from Georgia and East Florida.

The Monumento de la Constitucion, or Constitution Monument, is an 18-foot tall obelisk erected in the Plaza of St. Augustine in 1813.

The Treaty of Fort Jackson was signed on August 9, 1814 following the defeat of the Red Stick (Upper Creek) at the Battle of Horseshoe Bend.

The First Seminole War came to Florida when Jackson gathered 2,800 soldiers at Fort Scott and marched down the Apalachicola River.

The Adams-Onis Treaty of 1819 settled the land dispute between the United States and Spain. In this treaty Spain ceded Florida to the United States in exchange for $5 million dollars.

The Adams-Onis Treaty was officially proclaimed on February 22, 1821.

The Treaty of Moultrie Creek was signed on September 18, 1823 by representatives of the United States and the Seminole Indians.

In 1825, the U.S. Government renamed the Castillo. They chose "Fort Marion", after General Francis Marion, a Revolutionary patriot from South Carolina.