The Plaza de la Constitucion is a reminder of the brief time in 1813 that Spain had a constitutional government. In the center of the Plaza is the Monumento de la Constitucion. Many such monuments were built in 1813, but when the monarchy returned to Spain in late 1813, all monuments were ordered to be destroyed. City officials in St. Augustine did not comply, and as a result, this is believed to be the only such monument remaining in the world.

Originally erected in 1872 on private property on St. George Street by the St. Augustine Ladies Memorial Association, the confederate monument located in the plaza was rebuilt in the Plaza in 1879 reusing material from the original monument. The names of 46 Confederate war dead from St. Augustine are listed on the monument.

Mounted in the Plaza are two Civil War 32-pounder rifled cannons and two Civil War 8-inch Columbiad cannons from Fort Marion. The cannons were presented to the city by the U.S. War Department in 1900. In the adjacent Anderson Circle, there is a Civil War seacoast mortar from Fort Marion also given to the city by the U.S. War Department at about the same time.

Information provided by Florida Department of State.