Fort Rice was established on July 7, 1864, by General Alfred H. Sully as a field base during his 1864 expedition. It was named for Brigadier General James Clay Rice of Massachusetts, who was killed in battle during the Civil War. Fort Rice was the first in a chain of forts built to guard northern plains transportation routes, reflecting the United States government's changing policy toward western lands by encouraging settlement and providing protection for Euro-American settlers. It became an important military post on the Upper Missouri River. During the summer of 1864, Sioux in Dakota Territory were angered by military expeditions that had attacked Dakota, Lakota, and Yanktonai bands the previous year, and they increased attacks on transportation routes, including steamboats on the Missouri. In 1864, Sully returned with an army of 3,500 men to punish the Sioux, force them onto reservations, and strengthen peace by building military forts near the mouth of Long Lake Creek, at the confluence of the Yellowstone and Missouri Rivers, and near the mouth of the Powder River. The army hired fifteen steamboats to transport men and supplies part of the distance and retained three steamboats to support the expeditions for four months. Before leaving for the campaign that resulted in the Battle of Killdeer Mountain on July 28, 1864, Sully assigned Colonel Daniel J. Dill and soldiers of the Thirtieth Wisconsin Infantry to build the original Fort Rice. Because the construction season was late and more permanent building materials were lacking, the first fort consisted mainly of newly felled cottonwood log structures covered with sod and chinked with mud. The first permanent force, 537 men and one woman, arrived at Fort Rice on Monday, October 17, 1864. Tired, bedraggled, and sick, they were the 1st United States Volunteer Infantry, derisively called the Galvanized Yankees. These former Confederate prisoners of war, organized in six companies, had sworn a new allegiance to the Union Army and defended the fort until they were mustered out one year later. During that year, 102 soldiers and civilians, including one woman and one baby, died at or near the fort from causes including scurvy, diarrhea, typhoid, drowning, and a very few in combat. Life in the small frontier fort was difficult, with isolation caused by distance and a seasonally ice-bound transport system. During the first winter, the soldiers opened a theater, and from June 15 to October 9, 1865, they published a newspaper, the Frontier Scout.