The Port Hudson State Historic Site is located on the Mississippi River north of Baton Rouge in East Feliciana Parish, Louisiana, just outside the limits of Port Hudson and in the vicinity of Jackson. The site preserves a portion of the fortifications and battle area of the longest siege in American history, during the American Civil War from May 23 through July 9, 1863. The state of Louisiana maintains the site, which includes a museum about the siege, artillery displays, redoubts, and interpretive plaques. Historical reenactments are held each year. It was designated a National Historic Landmark in 1974, significant as the first place where African-American military units fought for the Union Army under African-American field leadership.