In this image, taken by photographer Isaac H. Bonsall, we see a partial artillery squad in a Federal redoubt, probably in Fortress Rosecrans at Murfreesboro, Tn. What is unique here is the gun. This appears to be an 8" Model 1861 Siege Howitzer mounted on a 24-pdr Siege Carriage. These resembled a cut down, fattened version of the familiar 3-inch Ordnance Rifle. Production began in 1862, when the Fort Pitt Foundry in Pittsburgh, Pennsylvania discontinued casting the Model 1841.