On May 2 1863, the day after the Confederates were defeated at the battle of Port Gibson, the Confederate Mississippi River battery at Grand Gulf fell into the hands of the Army of the Tennessee under Ulysses Grant . Grant had begun his campaign to take Vicksburg which lies 25 miles north.
I found this button on a bluff just south of Grand Gulf. On the internet I found the emblem to be the State seal of Wisconsin. I recently purchased "98 Days" by Warren Grabau, a book which details Grant's Vicksburg campaign. In it I found a passage that stated Grant dispatched 4 regiments from General Lauman's corps (which were then stationed in Memphis) to garrison Grand Gulf. One regiment was from Wisconsin, the 12th Wisconsin Volunteer infantry. I found a website dedicated to the 12th Wisconsin. On the website are letters and diaries from men in the regiment. The following is an excerpt from a letter sent by Sergeant Frank H. Putny to his father.
Letter of
Sergeant Frank H. Putney, Company G.
Grand Gulf, Mississippi May 22nd, 1863
When we were ordered here we came with the full expectation of marching to the front, and taking a hand in the big game being played before Vicksburg. But as it to confirm our previous experience, after waiting here two days, orders came for our Brig. to remain as a garrison to the place. We are camped on the bluff south of the old rebel fortifications in a very cool, airy, place, the best we have had in months, and are well content to stay.