Fort Clark was established on June 20, 1852, at Las Moras Springs in Kinney County by companies C and E of the First Infantry under the command of Maj. Joseph H. LaMotte. The name Las Moras ("the mulberries") was given by Spanish explorers to the springs and the creek they feed. The site was long favored by Coahuiltecan Indians and later by the Comanches, Apaches, and other tribes. During the late eighteenth and early nineteenth centuries the big spring was a stopping place on the eastern branch of the great Comanche Trail into Mexico. In 1849 Lt. W. H. C. Whiting, during his reconnaissance for a practicable wagon route between San Antonio and El Paso, recognized its military potential and recommended the location as a site for a fort. The post was originally named Fort Riley in honor of the commanding officer of the First Infantry, but on July 15, 1852, at Riley's request, it was renamed in honor of Maj. John B. Clark, a deceased officer who had served in the Mexican War. A formal military lease for Fort Clark was made on July 30, 1852, when Lt. Col. D. C. Tompkins signed an agreement with Samuel A. Maverick, who owned the land, for a period not to exceed twenty years. The fort was strategically located as anchor to the cordon of army posts that had been established along the southwest Texas border after the Mexican War. The fort's purpose was to guard the Mexican border, to protect the military road to El Paso, and to defend against Indian depredations arising from either side of the Rio Grande. By November 1852 Fort Clark had two companies of the First Infantry under the command of Capt. W. E. Prince, and for the next three years officers of the First Infantry and Mounted Rifles served as post commanders.
Bvt. Lt. Col. W. G. Freeman inspected Fort Clark on August 1, 1853, as a part of his tour of the Eighth Military Department, and reported it to be "a point of primary importance...from its salient position looking both to the Rio Grande and Indian frontiers." Freeman was the first to recommend the fort as being "well fitted for a Cavalry station." The quartermaster, according to Freeman, had only eight wagons available for hauling the materials needed to build the post. This was an inadequate number since the depot at Corpus Christi was 280 miles distant and wagons required thirty days, under favorable conditions, to make the round trip. Mail came to the post from San Antonio, "being brought weekly by special express." From their campsite near the spring and from tents pitched along the banks of Las Moras Creek, soldiers began construction of the fort on an adjacent high limestone ridge. The first barracks and houses were Mexican-type jacals and crude log huts of palisade construction. A few buildings of limestone, some of which are still standing, were begun in 1856–57. The ruins of the old post headquarters building has the date 1857 over the doorway. With the establishment of Fort Clark, a neighboring settlement of Las Moras came into existence when Oscar B. Brackett established a supply village for the fort. The town's name was changed to Brackett in 1856 and later to Brackettville. The stage from San Antonio to El Paso ran through the settlement, and for almost a century the town and the fort remained closely identified. In the summer of 1854 the Indian menace in Texas prompted Gen. Persifor F. Smith, the department commander, to make a requisition to Governor Elisha M. Pease for six companies of Texas Rangers to conduct a campaign against the raiders. Two companies of these Texas military volunteers, under captains Charles E. Travis and William Henry, were sent to Fort Clark, where they assisted the regulars in patrolling the road. Col. J. K. F. Mansfield inspected the post in early June 1856 and reported the presence of one company of the First Artillery and two companies of Mounted Rifles under the command of John Bankhead (Prince John) Magruder. Mansfield observed that although the adjutant's office, guardhouse, bakery, and magazine were built of stone, the other buildings were of log construction. He recommended that "stone quarters for the officers of these Companies be immediately commenced."
In February 1861 Texas voted to secede from the Union, and almost immediately state troops began demanding the surrender of United States posts in Texas. On March 19 Capt. W. H. T. Brooks, with three companies of United States Third Infantry, surrendered Fort Clark to a small company of the Provisional Army of Texas. In June 1861, after the outbreak of the Civil War, Fort Clark was garrisoned by companies C and H, Second Regiment of Texas Mounted Rifles, with Capt. H. A. Hamner as post commander. In August 1862 all Confederate troops were withdrawn from Fort Clark. After the war the fort was regarrisoned in December 1866 by Troop C, Fourth United States Cavalry with the task of protecting the road to El Paso. Although the post was dilapidated and required extensive repairs, a program for new construction was not begun, perhaps in part because the government was still leasing the land. In fact, a deed to the fort property was not secured until 1884, when Mary A. Maverick was paid $80,000 for the 3,965-acre tract. Despite efforts at patchwork repairs, more than five years went by before any significant progress was made. Between 1873 and 1875 most of the buildings, still in use in the historic district in 1990, were built of quarried limestone in an ambitious rebuilding project. A twenty-acre post was developed with the construction of barracks, officers' quarters, hospital, bakery, stables, and guardhouse. By 1875 the fort had quarters built of stone for more than 200 officers and men, including a commanding officer's house and eight officers' row duplexes accommodating sixteen families, as well as four previously built log quarters.
Especially significant during the Indian campaigns in the last half of the nineteenth century were the Black Seminole scouts, who served at Fort Clark from 1872 until 1914. The Black Seminoles had spent twenty years protecting the northern Mexican frontier state of Coahuila before being recruited by the United States Army to serve as scouts. Under Lt. John L. Bullis, who commanded them from 1873 to 1881, the scouts played a decisive role in the Indian campaigns. Among the roster of scouts are four who were awarded the Medal of Honor. During the Civil War the southwest Texas frontier was left relatively unprotected, and Indian depredations, particularly by Indians using Mexico as a sanctuary, were widespread and devastating. After the war attempts by federal troops to curtail Indian raiders coming from Mexico met with little success until early 1873, when Col. Ranald S. Mackenzie and the Fourth United States Cavalry were ordered to Fort Clark. On May 18 Mackenzie led six companies of the Fourth Cavalry, along with a contingent of Black Seminole scouts, across the border into Mexico on a punitive expedition against Kickapoo and Lipan Apache Indians at Remolino. It was a daring raid that resulted in the destruction of three villages, the killing of nineteen warriors, and the capture of forty prisoners, including the aged Lipan chief Costillitto. Despite Mexico's protests that the United States was violating its sovereignty, other sorties by Mackenzie soon followed. As a result, Indian forays from Mexico into Texas declined dramatically. Mackenzie was succeeded by Lt. Col. William Rufus Shafter in 1876. Shafter followed Mackenzie as one of the most successful of Fort Clark's Indian-fighting commanding officers. Under Shafter, Fort Clark became the garrison for the Tenth United States Cavalry and the Twenty Fourth Texas and Twenty Fifth Texas Infantry regiments. These were mounted regiments of Blacks, called Buffalo Soldiers by the Indians. The buffalo soldiers, for long mostly unacclaimed, left a distinguished record of service in ridding Southwest Texas of Indians.
Mackenzie's raid in 1873 had stopped Indian activity for almost three years, but, as the lesson of Remolino dimmed, violence once more came to the Rio Grande border area. In the fall of 1875 department commander Gen. Edward O. C. Ord established the District of the Nueces, with Fort Clark as headquarters and with Shafter in control. When, in April and May 1876, Lipan warriors killed twelve Texans in an unusually bloody raid, Ord authorized Shafter to go after the offenders in their Mexican villages. Shafter took five companies of cavalry, along with Bullis's scouts, and established a base camp near the mouth of the Pecos River. In the first of a long succession of border violations, Shafter's cavalrymen splashed across the Rio Grande and drove deep into the mountains of northern Coahuila. For two years Shafter's determined thrusts into Mexico in pursuit of the marauding Indians and their chief, Washa Lobo, aroused Mexican animosity and caused tensions between the United States and Mexican governments. Shafter's extensive campaign on the Texas borderlands frontier not only earned him the sobriquet "Pecos Bill" but boldly implemented the army's aggressive policy toward hostile Indians, which was one of removal or extermination. By the end of the decade the Indian problem along the border had finally been brought under control.
As the country became settled, the role of the fort was reduced to a routine of garrison duty and border patrol. In 1882 Gen. William T. Sherman, after making a tour of inspection, described Fort Clark as the "largest and most costly military post in Texas if not in the United States." Because of the new railroad being constructed nine miles south, he thought Fort Clark was obsolete and should be closed. The War Department decided otherwise, and, instead of closing the fort, launched a new program of construction and expansion. A large storehouse and granary, capable of holding 3,000 bushels of grain, was built. Three years later the eight officers' row duplexes were enlarged, and a new two-story bachelor officers' quarters was built on the site of the original post hospital. In 1888 a fine new duplex for staff officers was also added to the line of stone quarters on Officers' Row. During the late 1880s and early 1890s the fort was home for the Third Cavalry, the Eighteenth and Nineteenth Infantry, and occasional elements of the Seventh United States Cavalry. After the fort was again threatened with closure, it revived briefly during the Spanish-American War, when it was garrisoned by the Third Texas Infantry. With American entrance into World War I in 1917, a period of reconstruction and enlargement was begun that continued after the war ended. Many infantry regiments and practically all of the cavalry regiments were stationed at Fort Clark at various times. For twenty-one years, from 1920 to November 1941, Fort Clark was home of the Fifth Cavalry. The regiment, first organized in 1855 as the Second United States Cavalry, had been associated with the fort as early as 1856. Col. George S. Patton, Jr., served at Fort Clark in 1938 as regimental commander of the Fifth Cavalry.
At the outbreak of World War II the 112th Cavalry Regiment of the Texas National Guard, under command of Col. Julian Cunningham, was assigned to Fort Clark, where it trained until it was deployed for combat in the Pacific. Just before the 112th Cavalry left, the Black Ninth United States Cavalry arrived at Fort Clark from Fort Riley. Elements of the regiment had first served at Fort Clark in 1875, when the fort was a frontier outpost. In 1942 Col. William C. Chase and the 113th Cavalry Regiment spent a short stay guarding the Southern Pacific Railroad. On February 25, 1943, the Second Cavalry Division, the army's last horse-mounted unit, was activated under command of Maj. Gen. Harry H. Johnson. More than 12,000 troops were stationed there until their deployment in February 1944 to the European Theater of Operations. The war added another feature to the history of Fort Clark, that of having a German prisoner of war subcamp on the 4,000-acre reservation (see PRISONERS OF WAR). Finally, in June 1944, nearly three years after the beginning of World War II, and after full mechanization of the cavalry, the government ordered the closure of Fort Clark, one of the last horse-cavalry posts in the country. The fort was officially inactivated in early 1946, and later that year it was sold to the Texas Railway Equipment Company of Houston, a subsidiary of Brown and Root Company, for salvage and later use as a "Guest Ranch" (see DUDE RANCHING).
In 1971 Fort Clark was purchased by North American Towns of Texas and developed into a private recreation and retirement community. Since many famous officers served at Fort Clark, a number of the streets and buildings at the fort honor their names, including those of Mackenzie, Shafter, Bullis, Bliss, Wainright, and Patton. The Seminole-Negro Indian Scout Cemetery, where four Medal of Honor recipients have specially marked graves, may be visited on Farm Road 3348 west of the fort and three miles south of U.S. Highway 90. In 1990 Fort Clark encompassed about 2,700 acres. The large spring still fed Las Moras Creek, as well as the adjacent large swimming pool, which has sixty-eight-degree year-round water temperature. The grove of ancient oak and pecan trees next to the spring, where emigrants bound for California camped on the overland trail, is now a beautiful picnic area. Below the spring are seven miles of wooded creekfront. The historic district of the fort remains much as it was planned and built in the 1870s, with the old parade ground now a well-groomed par-three golf course. Much of the fort's military history is on display in the Old Fort Clark Guardhouse Museum, which is maintained by the Fort Clark Historical Society. In September 1979 Fort Clark was entered on the National Register of Historic Places.