In the Autumn of 1863 the Union Army advanced to Chattanooga forcing the Confederates to withdraw into Georgia. The 55,000 man Union force was led by General Rosecrans in pursuit of General Bragg's Confederates. In Georgia the Rebels were reinforced in strength to about 70,000 when troops arrived from Virginia. General Bragg then concentrated his forces against General Rosecrans' Army at Chickamauga.
The First Florida Cavalry, commanded by Colonel George Maxwell, was under Trigg's Brigade which was attached to Preston's Division. The brigade moved across Chickamauga Creek at daybreak on September 19, 1863 and formed a line near the Hunt House. This line was an extension of General Bate's battle line. Union artillery soon opened fire on the brigade from a battery on the right. Upon encountering heavy shot and shell the brigade advanced forward seeking cover beneath a hill. Colonel Maxwell was then ordered to move the First Florida Cavalry troops 300 yards in advance of the main brigade as skirmishers. They soon met heavy fire from Union infantry and artillery. The fight continued for nearly two hours in a corn field and adjacent woods until grape and canister shot forced the Regiment to withdraw.
The First Florida Cavalry rejoined the main brigade which was moved to support Brigadier General Robertson's troops under General Hood's Command. As Trigg's Brigade moved along a fenceline they were hit with cannon and rifle fire from well-entrenched Union positions. The brigade continued their advance, laying down heavy fire and eventually forced the enemy to withdraw in confusion. The First Florida Cavalry suffered two killed in action, fifteen wounded, and one missing. Lt. Richard Hart of Company E was among the dead.
The next morning, September 20, 1863, the brigade was sent to reinforce Manigault's Brigade. After encountering no enemy response to artillery fire, the brigade was then moved to support William's Artillery. After about two hours Colonel Trigg ordreed the First Florida Cavalry and the 7th Florida Infantry to pull back and provide a rear guard against an anticipated Union cavalry attack. When the Union attack failed to occur the 7th Florida rejoined the main brigade which was now engaging the enemy on a ridge. The First Cavalry was enroute to rejoin the brigade when the division commander, General Preston redirected it to support Gracie's Brigade. As the First Cavalry moved through the woods and fields they were hit with continuous rifle fire from enemy infantry entrenched along a ridge.
Upon reaching General Gracie, the First Cavalry was ordered to assault enemy breastworks on a hill. Gracie's Brigade, a larger force, had already been thrown back twice. Colonel Maxwell protested that his smaller force of First Cavalry troops could not be expected to accomplish the assault any better than Gracie. General Gracie then ordered Maxwell to keep his troops in the area until Gracie could locate and reorganize his brigade. The First Cavalry waited in position but was exposed to heavy fire. Maxwell then ordered the unit to fall back to the security of a fence line. They later joined in support of Gracie's troops in the assault at Snodgrass Hill. In this second day of combat the regiment lost one soldier killed and about nine wounded. Lt. Colonel William Stockton and Captain Gaston Finley were among the wounded.
By the evening of the second day the Confederates had caused the enemy to withdraw from the battlefield. Chickamauga, one of the most famous battles of the Civil War, had ended in a Confederate victory. However Bragg did not follow through his success against Rosecran and allowed the badly mauled Union Army to retreat into Chattanooga.

Personnel mentioned for gallantry are:

Higgenbothem, Madison
Tiner, E.J.
Goddard, Harvey J.
Herring, John W.

In addition to this listing Colonel Stockton mentions other casualties in a letter to his wife which may have been of the First Cavalry, or ther units within Colonel Trigg's Brigade at Chickamauga. He mentions killed, "Adler, Kennedy, Raull or Rawl and McRae". He wrote that "Whaley, Mcleve, Lt. Black and Lt. Milton were wounded", and that "Lt. Black had lost his leg". He said that "Allison" was missing in action. Col. Stockton claimed the regiment suffered a lost of about 33 soldiers. Col. Maxwell's report indicates 3 killed and 24 wounded, and research has identified by name 14 belonging to the First Florida Cavalry. Stockton was probably referring to his knowledge of both wounded and killed. Official reports estimate casualties for Trigg's Brigade at 46 KIA, 231 WIA, and 4 MIA. Although these figures are not exact, calcuations would suggest that the Regiment suffered less casualties than other Florida units under Trigg. The low casualty rate was the result of the First Cavalry being ordered to shift position frequently to support other units. This reduced the time engaged in offensive maneuvers, unlike the Sixth Florida which were continuously employed in offensive operations and experienced 35 killed and 130 wounded in the first day of battle.