He was aide successively to General Nathanael Greene and General Benedict Arnold and took part with the latter in the campaign against Quebec. On that strenuous expedition he first made the acquaintance of Aaron Burr. Unlike Burr he did not enjoy the distinction of having a general die in his arms, but his services were sufficiently noteworthy to lead to a promotion to lieutenant colonel.
The warrior’s next assignment was on the staff of General Horatio Gates who made him deputy adjutant general of the Army of the Northern Departments. It was then he first exhibited a fatal quality for appearing wherever intrigue was in the air. This instance was the Conway Cabal whose object was to cashier Washington and put Gates in his place. The Commander first got wind of it when Wilkinson, arriving in a garrulous mood at Lord Stirling’s headquarters, let out the contents of an incriminating letter from Conway to Gates. Wilkinson’s later version of the incident was that he deliberately made the disclosure. He was to develop an exceptional gift for shifting from the role of conspirator to patriot when the going got hot.
However deeply he may have been involved in the plot it did not interfere with his continued rise in the military. He was promoted to brigadier and appointed clothier-general of the American Army, but he neglected his work, drew a rebuke from Washington, and shortly thereafter resigned from the service.
Meanwhile Wilkinson had married Ann, daughter of John Biddle of Philadelphia, a merchant and innkeeper. His devotion to his wife was the one sincere and admirable feature of his life. He bought an estate in Pennsylvania and made a brief entry into local politics, serving as member of the State Assembly.
Like Burr, Wilkinson was extravagant, loved display, and lived beyond his means. In an age when heavy drinking was not uncommon his indulgence was sufficiently conspicuous to provoke comment. He was soon overwhelmed with debt and, following the example of many other men in the same predicament, decided to go west to recoup his fortunes. It was in Kentucky and the Southwest that he was destined to spend the rest of his life.
The Spaniards were then in possession of New Orleans, parts of the present Louisiana, the Floridas, Texas, and Mexico. They dreaded the crude American frontiersmen as the decadent Romans dreaded the Vandals and the Visigoths, expecting them at any time to swoop down, loot, destroy, and conquer. One of their defense measures was to seek out friends and informers among the Americans. In Wilkinson they found a willing collaborator. The Spaniards about this time closed the Mississippi to American goods coming down from the territories and the frontiersmen were indignant with the Spaniards—and with the indifference of their own government to their plight. It was then that the Spanish Plot took shape. Esteban Miro, Spanish Governor of Louisiana, fostered it by calling attention to the advantages to be gained by an establishment of a nation beyond the Alleghenies under the protection of Spain.
Wilkinson, one of the American leaders in the plot, saw the chance to turn Spanish fears to his account. He made two trips to New Orleans, ingratiated himself with Miro, and wrung from him a concession to deposit his goods at New Orleans and to enjoy other special commercial privileges. In return he swore allegiance to the Spanish crown and engaged to act as a secret agent. In the Spanish reports he was thereafter to be designated as “Number Thirteen.” It was a relationship Wilkinson was to maintain with Miro and his successors for more than a decade. The Spaniards agreed also to grant Wilkinson a pension of $2000 a year. But communications on the frontier were primitive; a pension payable in silver dollars did not always get through.
In spite of this new source of income Wilkinson’s extravagance kept him on the verge of bankruptcy. To add to his difficulties, the Spaniards reversed their policy and withdrew his trading privileges. Wilkinson was driven to selling most of his personal possessions. In this extremity he accepted a commission in the United States Army, took part as second in command in General Anthony Wayne’s invasion of the Wabash country, burned and pillaged with the best of them, and gained quite a reputation as an Indian fighter. At this time President Washington, making a summary of the general officers of the army, damned Wilkinson with faint praise, commenting that “little can be said of his abilities as an officer. He is lively, sensible, pompous and ambitious, but whether sober or not is unknown to me.”
Wayne learned of Wilkinson’s Spanish connections and warned the Government. When President Washington, toward the close of his administration, sent Andrew Ellicott out as commissioner to put into effect a treaty with Spain, he directed him to investigate Wilkinson. Ellicott did not at that time find reason to take the rumors seriously, but Wilkinson himself did. In alarm he wrote to Gayoso, governor of Natchez, “For the love of God and friendship enjoin great secrecy and caution in all our concerns. Never suffer my name to be written or spoken. The suspicion of Washington is wide awake.”
On the death of General Wayne in 1796 Wilkinson became senior officer in the army. Though John Adams, the incoming President, knew of Wayne’s charges against Wilkinson, he kept him on and gratified his suspicion with true New England frugality by holding him to the rank of brigadier.