Pleasonton was transferred to the Trans-Mississippi Theater and commanded the District of Central Missouri and the District of St. Louis on July 4, 1864.
He performed well and over a period of four days, defeated Gen. Sterling Price at the Westport, the Battle of Byram's Ford, the Battle of Mine Creek, and the Marais des Cygnes, ending the last Confederate threat in the West.
He was injured by a fall in October 1864.

In 1864 and 1865, he instituted a policy of amnesty, granting parole to Confederate prisoners on condition they go up the Missouri River to the Dakota and Montana Territories.
 This resulted in preventing many of the remnants of Price's army from becoming bushrangers, like Quantrill, and also resulted in Missouri Confederates migrating to the goldfields of the Montana Territory.

On April 10, 1866, President Andrew Johnson nominated Pleasonton for appointment as a brevet brigadier general in the regular army for the campaign in Missouri, to rank from March 13, 1865, and the U.S. Senate confirmed the appointment on May 4, 1866 (and July 14, 1866, after changes in the date of rank for brevet appointments for non-field service).
On July 17, 1866, President Johnson nominated Pleasonton for appointment as a brevet major general in the regular army for his overall conduct in the war, to rank from March 13, 1865, and the U.S. Senate confirmed the appointment on July 23, 1866.
Pleasonton was transferred to the Trans-Mississippi Theater and commanded the District of Central Missouri and the District of St. Louis on July 4, 1864. He performed well and over a period of four days, defeated Gen. Sterling Price at the Westport, the Battle of Byram's Ford, the Battle of Mine Creek, and the Marais des Cygnes, ending the last Confederate threat in the West. He was injured by a fall in October 1864.
In 1864 and 1865, he instituted a policy of amnesty, granting parole to Confederate prisoners on condition they go up the Missouri River to the Dakota and Montana Territories.  This resulted in preventing many of the remnants of Price's army from becoming bushrangers, like Quantrill, and also resulted in Missouri Confederates migrating to the goldfields of the Montana Territory.
On April 10, 1866, President Andrew Johnson nominated Pleasonton for appointment as a brevet brigadier general in the regular army for the campaign in Missouri, to rank from March 13, 1865, and the U.S. Senate confirmed the appointment on May 4, 1866 (and July 14, 1866, after changes in the date of rank for brevet appointments for non-field service). On July 17, 1866, President Johnson nominated Pleasonton for appointment as a brevet major general in the regular army for his overall conduct in the war, to rank from March 13, 1865, and the U.S. Senate confirmed the appointment on July 23, 1866.
Alfred Pleasonton