Fighting as part of the Army of Tennessee in the Western Theater of the American Civil War it was surrendered on April 26, 1865.

On January 6, state militia occupied the Apalachicola Arsenal at Chattahoochee and the following day the Fort Marion in St. Augustine.

on May 5, 1861, men from the counties of Leon, Alachua, Madison, Jefferson, Jackson, Franklin, Gadsden, and Escambia were mustered into state service as the 1st Florida Infantry Regiment.

[3] On October 9, 1861, a detachment of 180 men from all companies of the regiment participated in the unsuccessful attempt to capture Fort Pickens.

When the service time of the regiment came to its end it failed to reorganize in early 1862 when only 300 of the remaining 600 men, enough for four companies, reenlisted.

[12] Going north in the Confederate Heartland Offensive the 1st Battalion fought in the Battle of Perryville, suffering 12 dead, 54 wounded and 6 missing from a total of 167 men.

In December 1862 the regiment, now part of the brigade of Brigadier William Preston, was loosely paired with the 3rd Florida Infantry, under the overall command of Miller.

[14] The 531 men of the 1st and 3rd Regiments fought distinctively at Stones River, taking high losses including Colonel Miller, who was wounded on the last day of the battle.

Stationed near Glass' Mill; the 1st-3rd Florida was detached with an artillery battery as observation force when the rest of the division moved southwards.

The 1st-3rd, relieved by cavalry from Wharton's division, had to march the whole night till it reached its position on the right; not locating its brigade till 8 a.m.[18] When the advance against the Union positions around Horseshoe Ridge started in the morning the brigade was on the right of the second line, and marched against elements from Thomas' XIV Corps.

Advancing towards Kelly Field along the Lafayette Road in a southern move, the 1st-3rd Florida, together with the 47th Georgia Infantry, was separated from the rest of the column and drifted rightwards.

Then the division shifted its northern elements to the east due to the advance of Gordon Granger's Reserve Corps from the north.

[19]When the battle ended in a victory for the South, the Army of Tennessee received the gratitude of their superiors; and the 1st-3rd Florida had 18 of its men put on the Confederate Honor Roll.

Parts of the brigade fought in General William B. Bate's makeshift rear-guard and Brigadier Finley receive praise for his command.

[29] When the 1st-3rd Florida went with General John Bell Hood into the terrible winter campaign of Franklin-Nashville the command quickly went to Cpt.

[30][31] When General Nathan B. Forrest and his cavalry were dispatched to raid the area it was accompanied by Bate's division, including the Florida Brigade.

[33] When Johnston surrendered at Bennett Place on April 26 the 1st Florida, and so all Floridian units in the Army of Tennessee, had fewer than 200 men present and fit for duty (with just over 400 total).