The guiding force behind the creation of the two regiments of United States Sharpshooters was New York inventor and crack rifleman Hiram Berdan. For a decade and a half before the war he had been the acknowledged top marksman in the country, and his inventions included a musket ball and a repeating rifle.
In the summer and fall of 1861 he was involved in the recruiting of 18 companies, from eight states, which were formed into two regiments. His assignments included: colonel, 1st United States Sharpshooters (November 30, 1861); commanding 2nd Brigade, 3rd Division, 3rd Corps, Army of the Potomac (February 19-March 1863); commanding 3rd Brigade, 3rd Division, 3rd Corps, Army of the Potomac (March 13 - June 20, 1863); and commanding 2nd Brigade, 1st Division, 3rd Corps, Army of the Potomac (July 2-7, 1863).
His men, who had to pass rigorous marksmanship tests, were dressed in distinctive green uniforms and equipped with the most advanced longrange rifles equipped with telescopic sights. Even when assigned to a brigade, the regiments were usually detached for special assignments on the field of battle. They were frequently used for skirmish duty.
Berdan fought at the Seven Days and 2nd Bull Run. In 1865 he was awarded the brevets of brigadier and major general for Chancellorsville and Gettysburg, at each of which he led a brigade. He resigned on January 2, 1864. He was considered by many to be a crack marksman but unfit for a command. Berdan subsequently invented numerous engines of war. (Stevens, C.A., Berdan's United States Sharpshooters in the Army of the Potomac, 1861-1865)
Source: "Who Was Who In The Civil War" by Stewart Sifakis