Clark's military achievements all came before his 30th birthday. Afterwards, he was disgraced and accused of being drunken on duty and therefore left Kentucky to live on the Indiana frontier. Never fully reimbursed by Virginia for his wartime expenditures, he spent the final decades of his life evading creditors, living in increasing poverty and obscurity, and often struggling with alcoholism. He was also involved in two failed conspiracies to open the Spanish controlled Mississippi River to American traffic. After suffering a stroke and losing his leg, he was aided in his final years by family members, including his younger brother William, one of the leaders of the Lewis and Clark Expedition. Clark died of a second stroke on February 13, 1818.
Little is known of Clark's schooling, but he went to live with his grandfather so he could attend Donald Robertson's school with James Madison and John Taylor of Caroline and received a common education. He was also tutored at home, as was usual for Virginian children of the period, eventually becoming a farmer and being taught to survey land by his father.
At age nineteen, Clark left his home on his first surveying trip into western Viriginia. In 1772, as a twenty-year-old surveyor, Clark made his first trip into Kentucky via the Ohio River at Pittsburgh, one of thousands of settlers entering the area as a result of the Treaty of Fort Stanwix of 1768. In 1774, Clark was preparing to lead an expedition of ninety men down the Ohio River when war broke out with the American Indians. The tribes living in the Ohio country had not been party to the treaty signed with the Cherokee, which ceded the Kentucky hunting grounds to Britain for settlement. The violence that resulted eventually culminated in Lord Dunmore's War, in which Clark played a small role as a captain in the Virginia militia.
In July 1778, Clark and about 175 men crossed the Ohio River at Fort Massac and marched to Kaskaskia, taking it on the night of July 4. Cahokia, Vincennes, and several other villages and forts in British territory were subsequently captured without firing a shot, because most of the French-speaking and American Indian inhabitants were unwilling to take up arms on behalf of the British. To counter Clark's advance, Henry Hamilton reoccupied Vincennes with a small force. In February 1779, Clark returned to Vincennes in a surprise winter expedition and retook the town, capturing Hamilton in the process. The winter expedition was Clark's most significant military achievement and became the source of his reputation as an early American military hero. When news of his victory reached General George Washington, his victory was celebrated and was used to encourage the alliance with France. Washington considered his victory a great success, especially considering he had received nearly no support from the regular army in men or funds. Virginia also capitalized on Clark's success and laid claim to the whole of the Northwest by establishing the region as Illinois County, Virginia.
An even more extensive defeat was to follow the next year: in August 1782, another British-Indian force defeated the Kentucky militia at the Battle of Blue Licks. Although he had not been present at the battle, Clark, as senior military officer, was severely criticized in the Virginia Council for the disaster. In response, Clark led another expedition into the Ohio country, destroying several Indian towns along the Great Miami River in the last major expedition of the war.
The importance of Clark's activities in the Revolutionary War has been the subject of much debate. As early as 1779 he was called the Conquerer of the Northwest by George Mason. Because the British ceded the entire Northwest Territory to the United States in the 1783 Treaty of Paris, some historians, including William Hayden English, credit Clark with nearly doubling the size of the original Thirteen Colonies by seizing control of the Illinois country during the war. Clark's Illinois campaign—particularly the surprise march to Vincennes—was greatly celebrated and romanticized. Other historians, such as Lowell Harrison, have downplayed the importance of the campaign in the peace negotiations and the outcome of the war, arguing that Clark's "conquest" was little more than a temporary occupation.
Clark was just thirty years old when the Revolutionary War ended, but his greatest military achievements were already behind him. Ever since Clark's victories in Illinois, settlers had been pouring into Kentucky, often illegally squatting on Indian land north of the Ohio River. From 1784 until 1788 Clark served as the superintendent-surveyor for Virginia's war veterans and surveyed the lands granted to them for their service in the war. The position brought a small income, but Clark devoted very little time to the enterprise. Clark helped to negotiate the Treaty of Fort McIntosh in 1785 and the Treaty of Fort Finney in 1786 with tribes north of the river, but violence between Native Americans and Kentucky settlers continued to escalate.
According to a 1790 U.S. government report, 1,500 Kentucky settlers had been killed in Indian raids since the end of the Revolutionary War. In an attempt to end these raids, Clark led an expedition of 1,200 drafted men against Indians towns on the Wabash River in 1786, one of the first actions of the Northwest Indian War. The campaign ended without a victory: lacking supplies, about three-hundred militiamen mutinied, and Clark had to withdraw, but not before concluding a ceasefire with the Indians. It was rumored, most notably by James Wilkinson, that Clark had often been drunk on duty. When Clark learned of the rumors he demanded an official inquiry be made, but his request was declined by Governor of Virginia, and Viriginia Council condemned Clark's actions. Clark's reputation was tarnished, he never again led men in battle and left Kentucky, moving into the Indiana frontier near Clarksville
Clark lived most of the rest of his life in financial difficulties. Clark had financed the majority of his military campaigns with borrowed funds. When creditors began to come to him for these unpaid debts, he was unable to obtain recompense from Virginia or the United States Congress because record keeping on the frontier during the war had been haphazard. For his services in the war Viriginia gave Clark a gift of 150,000 acres of land. The soldiers who fought with Clark also received smaller tracts of land. Together with Clark's Grant and his other holdings, his ownership encompassed all of present day Clark County, Indiana and most of the surrounding counties. Although Clark had claims to tens of thousands of acres of land resulting from his military service and land speculation, he was "land-poor", i.e. he owned much land but lacked the means to make money from it.
With his career seemingly over and his prospects for prosperity doubtful, on February 2, 1793, Clark offered his services to Edmond-Charles Genêt, the controversial ambassador of revolutionary France, hoping to earn money to maintain his estate. Western Americans were outraged that the Spanish, who controlled Louisiana, denied Americans free access to the Mississippi River, their only easy outlet for long distance commerce. The Washington Administration was also seemingly deaf to western concerns about opening the Mississippi to U.S. commerce. Clark proposed to Genêt that, with French financial support, he could lead an expedition to drive the Spanish out of the Mississippi Valley. Genêt appointed Clark "Major General in the Armies of France and Commander-in-chief of the French Revolutionary Legion on the Mississippi River. Clark began to organize a campaign to seize New Madrid, St. Louis, Natchez, and New Orleans, getting assistance from old comrades such as Benjamin Logan and John Montgomery, and winning the tacit support of Kentucky governor Isaac Shelby. Clark spent US$4,680 of his own money for supplies. In early 1794, however, President Washington issued a proclamation forbidding Americans from violating U.S. neutrality and threatened to dispatch General Anthony Wayne to Fort Massac to stop the expedition. The French government recalled Genêt and revoked the commissions he granted to the Americans for the war against Spain. Clark's planned campaign gradually collapsed, and he was unable to have the French reimburse him for his expenses.
Due to his growing debt, it became impossible for Clark to continue holding his land which became subject to seizure. Much of his land was deeded to friends or transferred to family members where it could be held for him, rather than lost to the creditors. After a few years, the lenders and their assigns closed in and deprived the veteran of almost all of the property that remained in his name. Clark, once the largest landholder in the Northwest Territory, was left with only a small plot of land in Clarksville, where he built a small gristmill which he worked with two African American slaves. Clark lived on for another two decades, and continued to struggle with alcohol abuse, a problem which had plagued him on-and-off for many years. He was very bitter about his treatment and neglect by Viriginia, and blamed his misfortune on them.
The Indiana Territory chartered the Indiana Canal Company in 1805 to build a canal around the Falls of the Ohio, near Clarksville. Clark was named to the board of directors and was part of the surveying team that assisted in laying out the route of the canal. The company collapsed the next year before construction could begin, when two of the fellow board members, including Vice President Aaron Burr, were arrested for treason. Burr was plotting to seize Louisiana from Spain and open the Mississippi to the Americans. A large part of the company's $1.2 million in investments was unaccounted for, and where the funds went was never determined.
In 1809, Clark suffered a severe stroke. Falling into an operating fireplace, he suffered a burn on one leg so severe as to necessitate the amputation of the limb. It was impossible for Clark to continue to operate his mill, so he became a dependent member of the household of his brother-in-law, Major William Croghan, a planter at Locust Grove farm eight miles (13 km) from the growing town of Louisville. During 1812, the Viriginia General Assembly granted Clark a pension of four-hundred dollars per year, and finally recognized his services in the Revolution by granting him ceremonial sword. After a second stroke, Clark died at Locust Grove, February 13, 1818, and was buried at Locust Grove Cemetery two days later Clark's body was exhumed along with the rest of his family members on October 29, 1869, and reburied at Cave Hill Cemetery in Louisville.
Several years after Clark's death the state of Virginia granted his estate $30,000 as a partial payment on the debts that they owed him. The government of Vigirinia continued to find debt to Clark for decades, with the last payment to his estate being made in 1913. Clark never married and he kept no account of any romantic relationships, although his family held that he had once been in love with Teresa de Leyba, sister of Don Fernando de Leyba, the Spanish Governor of Louisiana. Writings from his niece and cousin in the Draper Manuscripts attest to their belief in Clark's lifelong disappointment over the failed romance.
Other statues of Clark can be found in:
Places named for Clark include:
And finally, schools named after Clark include: