After Texas seceded from the Union on March 2, 1861, and joined the Confederate States of America, Confederate training grounds and Union prisoner of war camps were established in the area. Camp Felder was established as a cavalry base on the plantation of Gabriel Felder, a wealthy planter originally from Mississippi whose land lay along New Years Creek. The camp was in use as early as November 6, 1863, by Andrews' Company, Waller's Regiment of Cavalry, and by February 1864 it was serving as the headquarters of Company K of McCord's Frontier Regiment. In the fall of 1864, Camp Groce, which held Federal prisoners captured in Louisiana at the Battle of Calcasieu Pass and in South Texas, became overcrowded after additional prisoners were moved there from Camp Ford in Tyler. In September, a yellow fever outbreak led to the evacuation of the entire prison population, which made its way to Camp Gillespie. Around 500 prisoners arrived at Camp Felder on October 3, 1864, and remained there for the rest of the month. Like other prison camps, Camp Felder had no shelter, and prisoners were kept in the open between two hills beside Peach Creek and its tributaries. Because of the yellow fever outbreak and the harsh conditions at Camp Felder, many Union prisoners died there, as did at least two Confederate guards; although the exact total is unknown, estimates range from 43 to 78 deaths. The prisoners were moved back to Camp Groce in November after the outbreak subsided.