He married Jane Herbert Wilkinson Long in 1815, settled in Natchez, Mississippi, after the war, and served as a doctor at Port Gibson, Mississippi|Port Gibso].
It aroused such strong opposition in Natchez that prominent citizens planned a filibustering expedition to conquer Spanish Texas and placed Long in command.
[2] The rhetoric surrounding their first expedition received a great deal of attention, and about 200 men including Jim Bowie and Ben Milam gathered in Natchez in early 1819 for the planned invasion of Texas.
His army eventually grew restless and many men returned to the United States, and a Spanish expedition routed Long and his remaining followers in October 1819.
He was transported to Mexico City in March 1822 to plead his case before Mexican President Agustín de Iturbide, but on April 8, 1822, he was shot and killed by a guard.