The Battle of Plains Store was fought on May 21, 1863, in East Baton Rouge Parish, Louisiana, during the campaign to capture Port Hudson in the American Civil War.

Union troops advancing from Baton Rouge, Louisiana, clashed with 600 Confederates at a road junction.

[2] Other Union troops commanded by Major General Nathaniel Banks had been moving towards Shreveport, Louisiana, but instead turned towards Port Hudson to capture it.

Banks's goal was to defeat the Confederate force there led by Major General Franklin Gardner and then drive north to aid the attack on Vicksburg.

[3] In support of Banks, a Union division led by Major General Christopher C. Augur left Baton Rouge, Louisiana, and moved north towards Port Hudson[1] on May 20[4] with 3,500 men.

[6] On the morning of May 21, Augur's leading forces, commanded by Colonel Benjamin H. Grierson, met Confederate troops near the junction of the Plains Store and Bayou Sara roads.

[1] Historian John D. Winters states that the Confederates suffered 89 men killed, wounded, or missing, and the Union 100.

[1] On May 22, Banks landed troops at Bayou Sara and pushed forward, having heard that Augur had met resistance.

More Union troops arrived from New Orleans, Louisiana, and by the end of the day, Port Hudson was almost completely surrounded.

[15] Johnston again ordered Gardner to withdraw the next day, but by that point the Confederates in Port Hudson were cut off.