Passage: During the Civil War, the tide of new miners into the territory slowed to a trickle, and many left for the East to fight. The Missourians who stayed formed two volunteer regiments, as well as home guard. Although seemingly stationed at the periphery of the war theaters, the Colorado regiments found themselves in a crucial position in 1862 after the Confederate invasion of the New Mexico Territory by General Henry Sibley and a force of Texans. Sibley's New Mexico campaign was intended as a prelude to an invasion of the Colorado Territory northward to Fort Laramie, cutting the supply lines between California and the rest of the Union. The Coloradans, under the command of Union Army General Edward Canby and Colonel John P. Slough, Lt. Col. Samuel F. Tappan and Major John M. Chivington, defeated Sibley's force at the two day  Battle of Glorieta Pass along the Santa Fe Trail, thwarting the Confederate strategy.

Question: How many volunteer regiments did the Missourians form?
two