Composed of volunteers from the Mississippi Gulf Coast, the 3rd Regiment was initially assigned to coastal defense, before taking part in numerous campaigns of the Western theater of the American Civil War.

The 3rd Regiment was organized in August 1861 at Bay St. Louis, originally for state service, composed of volunteer companies mostly from the Mississippi Gulf Coast region.

[2] The 3rd took part in the Meridian campaign opposing Union General William T. Sherman's march across Mississippi, and was then transferred to Georgia in 1864.

During the Atlanta Campaign, the 3rd Regiment fought at New Hope Church, Kennesaw Mountain, and Peachtree Creek before the city was captured by Union forces.

In his after-action report describing the fighting at Kennesaw Mountain, General Featherston wrote that the "Third Mississippi Regiment acted with great coolness, courage, and determination".