There was no captain named Vicksburg in the civil war, so no person of that name could have been important to the union or anybody else. Perhaps you are thinking of the battle of Vicksburg, which was critical.
Vicksburg is the most important Union victory.
Victory at Vicksburg secured control of the Mississippi Valley for the Union.
They have burg at the end
Gettysburg; Vicksburg; Appomattox , Antietam ,Shiloh
battle of vicksburg and gettysburg
Vicksburg was so important because you had to control that city to control the Mississippi River, other wise no matter what else the union controlled, the Mississippi was worthless.
The Battle of Vicksburg gave the Union control of the Mississippi River.
US Naval commander Samuel P. Lee was the first Union commander to demand the surrender of Vicksburg Mississippi. This demand was made on May 18, 1862. Lee was the captain of the USS Oneida. Just prior to this the City of New Orleans was captured and Baton Rouge also fell. The Union navy then set its sights on Vicksburg.
That would be the Siege of Vicksburg.
The Union could control the Mississippi River from Vicksburg
Vicksburg - U.S. Grant (Union) Gettysburg - George Meade (Union)
It was very important to the Union army, because the battle cut off Arkansas, Texas and Louisiana from the Confederate army.