Major General John Charles Frémont led US troops in California and had forged an army of crack troops who were experienced in war (the Mexican-American War), exploration, fighting Indians, hunting buffalo, and settlements in the West. The Civil War called him back to Missouri, where he commanded the Department of the West. In 1862, Frémont was assigned to the mountainous area of Virginia and what would later be West Virginia. He formed a unit consisting of a few dozen of his best fighters who called themselves Jessie Scouts, after Frémont's wife, who was considered to be smarter than her husband.
The Jessie Scouts used spy tactics to infiltrate Confederate units, which meant wearing Confederate uniforms, concocting false identities, perfecting a certain speaking style, and in at least one case, passing as a woman. They memorized code to recognize and communicate with each other while embedded with Confederates. Being found by Union soldiers could get them arrested, and being exposed to the Confederates would get them killed. Read the dangerous but crucial exploits of the Jessie Scouts at CrimeReads. -via Damn Interesting