Fort Jefferson (also known as Camp Crittenden) was the second of two Union Army posts established in Ballard County in September 1861, following the Confederate occupation of Columbus. Fort Jefferson was first established during the American Revolution by George Rogers Clark in 1780 and occupied until 1781. The Civil War era fort was located on the same site, just above the mouth of Mayfield Creek. The first post was Fort Holt, named for Joseph Holt, Secretary of War at the end of the Buchanan administration and after March 1862 the first Judge Advocate General of the U.S. Army. Holt was born in Breckinridge County, Kentucky in 1807 and practice law in Louisville before becoming Commissioner of Patents in 1857. Fort Holt was located opposite Birds' Point, Missouri. The two forts were part of the defense of the confluence of the Ohio and Mississippi rivers and the shipyards at Mound City, Illinois.
Before establishment of the two forts, Union troops were active in Ballard County. On June 5 and 6, 1861, a small force was observed checking on rebel activity, and again on August 21, 1861.
By late September 1861, there were 3,595 federal troops at Fort Holt and more than 2,000 at Fort Jefferson. Refugees, mostly former slaves, flooded Union lines soon after the forts were established. They were put to work by General Grant on the fortifications at Fort Holt and worked felling trees and digging earthworks.
Troops from Fort Jefferson and Fort Holt were sent to Elliott's Mill and involved in skirmishes and reconnaissance in late September 1861. Fort Holt troops later went on a September 26 raid on Blandville and arrested secessionists on September 26. All the troops from Fort Holt went with General Grant and fought in the Battle of Belmont.
Most of the troops from Forts Holt and Jefferson accompanied General Grant to Forts Henry and Donelson as the western theatre moved east and south. On January 10, 1862 Federal troops were sent to Fort Jefferson as a diversion to distract Confederates at Forts Henry and Donelson.
Much of the action seen by both forts involved river boats. A naval skirmish occurred near Fort Jefferson at Lucus Bend on the Mississippi River, September 9 and 10, 1861. The USS Conestoga defeated the CSS Yankee, but returned to Cairo under heavy sniper fire from both sides of the river. The largest skirmish occurred on January 11, 1862 at Lucas Bend. Confederate gunboats attacked the USS Essex and the USS St. Louis. After twenty minutes of artillery exchanges and an hour-long running battle there was no clear winner. This encounter was the last time the Confederate Navy approached this far north.
By April 1862, both of these forts were deserted, Fort Holt having been flooded out in the spring. Federal forces in far western Kentucky concentrated at Columbus and Paducah.