The plunge to Civil War exploded on April 12, 1861, in the bombardment of Fort Sumter in Charleston Harbor. When it became apparent the conflict would not be short, the Army began removing regular soldiers from the District of Oregon. Because of the responsibility to guard the reservations and maintain a military presence, especially in central and eastern Oregon where gold discoveries generated a rapid influx of miners and settlers, federal and state officials scrambled to find replacement troops. The Department of the Pacific raised recruits and dispatched companies of California Volunteers to Fort Yamhill, Fort Hoskins, and Siletz Blockhouse. The Army abandoned Fort Umpqua in 1862. The First Oregon Volunteer Cavalry and the First Washington Territory Infantry went to central Oregon. During the Civil War, Oregon raised six companies of cavalry. Known officially as the First Oregon Cavalry, they served until June, 1865.
Secessionist sympathizers surfaced in Oregon. The Knights of the Golden Circle, an anti-Union group, reportedly plotted the seizure of Fort Vancouver, military headquarters on the Columbia River. They did not act. When pro-Confederate partisans raised their flag in Jacksonville, they faced opposition and backed down. The Long Tom Rebellion was perhaps the most noteworthy outbreak of secessionist feeling. Emboldened by the assassination of President Lincoln, Philip Henry Mulkey walked the streets of Eugene on May 6, 1865, shouting: "Hurrah for Jeff Davis, and damn the man that won't!" The First Oregon Volunteer Infantry arrested Mulkey, who promptly grabbed a glass of water and toasted Jeff Davis, the Confederate president. A pro-Union mob, wanting to lynch Mulkey, broke down the jail door. Mulkey slashed one of the men with a hidden knife. Mulkey's supporters from the Long Tom district were ready to fight, but the infantry slipped Mulkey out of town under an armed guard, loaded him on a steamboat, and sent him off to three months in jail at Fort Vancouver. Mulkey sued for $10,000 for false arrest. After 14 court appearances over a two-year period, he settled for $200.
For many soldiers the Civil War in Oregon was a monotonous, numbing assignment. In their monthly post returns, officers recorded desertions, suicides, and bouts in the brig because of drunkenness and misbehavior. The Indians were quiet on the Siletz and Grand Ronde Reservations. The rain was predictable and depressing. "Nothing transpired of importance," recorded Royal A. Bensell, a soldier at Fort Yamhill. Too many days brought that refrain in his Civil War diary.
East of the Cascades the troops had active engagement. Gold discoveries at Canyon City and other diggings on the headwaters of the John Day River and in the Powder River country on the eastern slopes of the Blue Mountains had drawn thousands of miners. The Northern Paiute, disrupted in their seasonal round and tempted by the easy pickings of clothing, food, and horses, embarked on raids and conflicts that demanded military intervention. The Oregon Volunteer Infantry and Cavalry established Camp Watson (1864) after placing troops at temporary stations: Dahlgren, Currey, Gibbs, Henderson, and Maury. The forces engaged in lengthy and often fruitless explorations searching for the elusive Indians.
Realizing that the problems east of the Cascades were of long duration, the U.S. Army established Fort Klamath (1863), Camp Warner (1866), and Fort Harney (1867). During the summer of 1864 Captains John M. Drake and George B. Curry and Lieutenant-Colonel Charles Drew led troops on sweeps through southeastern Oregon, northern Nevada, and southwestern Idaho. They had little success finding the "enemy." "These tribes can be gathered upon a reservation, controlled, subsisted for a short time, and afterwards be made to subsist themselves," commented the superintendent of Indian affairs, "for one-tenth the cost of supporting military forces in pursuit of them." In time that happened. The Klamath Reservation and the short-lived Malheur Reservation included various bands of Northern Paiute. The Civil War in Oregon mostly involved guarding reservations or pursuing native peoples who were masters of escape in their own homelands.