In September, 1861, a Company of Sharpshooters was recruited at Battle Creek, Hartford, Lawrence, Keeler, Watervliet, Benton Harbor and St. Joseph by John Piper, Albert S. Gove, Stephen Duncombe and Philip C. Dedrick. They offered their services to Major General John C. Fremont, who ordered them to Benton Barracks, St Louis, Missouri, where they were assigned to Company D, of Birge's Sharpshooters and mustered into the service of the United States on September 9, 1861.There were also men in Companies B, C, E and F of the regiment which was under the special patronage of General Fremont who intended to make it a model Sharpshooting Regiment and one that would represent the whole West. With this view, recruiting offices were appointed in nearly all Western States to recruit for Birge's Sharpshooters. Two Companies were raised in Ohio, three in Illinois, one in Michigan and three were organized at the barracks by squads sent by recruiting officers from Iowa, Minnesota and other Western States, thus forming a Regiment different from any other than this one, in that it represented every State in the West. Commenced under the most favorable auspices, it would have been, before taking the field, a large and splendidly equipped organization had not Fremont been suspended from command of the Department. His pet scheme was of a complete Regiment of Sharpshooters was partially squelched by General Halleck, who stopped all recruiting for it and hurried them into the field before they were thoroughly equipped and organized, with but nine companies, which was below the minimum requirement for a Regimental organization. They were armed with the American Deer and Target Rifle. The accoutrements were not the kind prescribed by army regulations; but, consisted of a bullet pouch of Bear skin covering and a powder horn, or in some cases a flask. In the bullet pouch was a compartment where the soldier carried his screw drivers, bullet molds and patch cutter, singular implements for a soldier; but, Birge's boys molded their own bullets, greased them and patched them with as much care as an old hunter would and used them as effectively. It was the design of General Fremont to give them a complete hunter dress; but, this was vetoed by Halleck and the only thing peculiar about the dress was the hat, which was a Gray sugar loaf affair, with three squirrels tails running from both front and back and meeting at the apex of the crown in an indescribable knot.
Lieutenant Colonel John M. Birge, of St Louis, commanded the Regiment and on the 12th of December, 1861, marched them from Benton Barracks to take the field in Northern Missouri. Arriving at Centralia, on the North Missouri Railroad, the Colonel found plenty of work for his little command which he scattered in detachments over the country in search of the Confederates, several small bodies of whom were met and defeated, besides being frightened by the squirrel Tail hats and the long range rifles.
On the 28th of December, General Prentiss, commanding the district of North Missouri, led four companies of Curtis's Horse and four companies of Sharpshooters, Company D being one of the four, against the command of Colonel Dorsey, consisting of nearly a thousand mounted and dismounted Infantry. General Prentiss's command numbered about 400 men; but, so impetuously did they fight that in less than an two hours the Southerners was routed, "foot, horse and dragoon". This battle was a Mount Zion Church, twenty miles from Sturgeon and has been known as the battle of Mt. Zion. After this battle no fighting of any moment occurred during their stay in North Missouri, which terminated on the 4th of February, 1862 on which day the command was shipped by railroad to St Louis where they embarked on a ferry to Fort Henry, arriving on the 9th, just too late to take part in the capture of the Fort. Here the Regiment was attached to Colonel Lauman's Brigade of General C.F. Smith's Division and marched with them on the 12th to a position in front of Fort Donelson.
Here the General was a little perplexed to know what to do with a Regiment armed with Deer rifles, without bayonets and did a terrible amount of swearing because the Regiment was armed with that type of rifle; but, finally concluded to let them fight in their own way.
And thus it was that during the memorable siege, the "Squirrel Tails" scattered themselves out, behind logs, trees and stumps, in trees and clumps of bushes along the entire front of Smith's Division. Every man kept a sharp look out for the Confederates and with a steady hand kept an entire 12 gun Battery in front of the Division silent for the entire 3 days of the siege.
Remaining at Fort Donelson after its capture until March 5th, the command marched back again to the Tennessee River and embarked for Pittsburgh Landing, where they landed on the 18th of the same month. On the 6th and 7th of April the participated in the Battle of Shiloh; but, being used only as a skirmishing Regiment, their loss was small compared with some other Regiments. From the 10th of May to the 30th, in the siege of Corinth, Ms, they were kept busy skirmishing almost constantly and during that time lost a large number of men.
Upon returning to Corinth from the pursuit of the retreating Southern Forces, P.E. Burke took command of the Regiment, having been commissioned a Colonel, Colonel Birge having been mustered out. They were assigned to the City command as Provost Guard, remaining till the 3rd and 4th of October, where they lost heavily in men and officers. From Corinth, in pursuit of the fleeing Confederates once again, and back to Rienzi, Ms, consumed some weeks, and the 26th of November found the Company encamped 6 miles South of Corinth, where they helped establish a fine stockade camp, called after an old commander, General Davies. While here the Regiment which had heretofore belonged to Missouri, was transferred, by order of the Secretary of War, to Illinois. The name Birge's Sharpshooters was dropped entirely and henceforth the Regiment was officially the 66th Illinois Sharpshooters or Western Sharpshooters.
Here the Regiment purchased, with their own funds, at a cost of $30 each, the Henry Repeating Rifle. This arm did much to make the Regiment famous and the men, who purchased them with their own means, deserve great credit.
The Regiment remained at this camp until the 12th of November, 1863, when the Division-then the 2nd Division, 16th Army Corps-moved to Pulaski, Tn. Here in December the Company re-enlisted and in January, 1864, were sent to Chicago to be given Veteran furlough. After being re-organized as a Veteran Company and Regiment, they returned to Pulaski, where on the 29th of April started for Chattanooga, 600 strong to enter with the Grand Army upon the Atlanta Campaign.
Leaving Chattanooga on the 6th of May, the Regiment had the honor, on the 9th of the same month, to open the fighting of the Army of the Tennessee in this campaign, at Snake Creek Gap and Resaca, and unaided and almost unsupported captured and held till night the heights in front of the stronghold of Resaca.
From here throughout the whole of that memorable campaign these companies were always in front and participated in not less than 10 pitched battles and innumerable skirmishes, Company D losing its Captain, 2 Lieutenants and 10 to 15 enlisted men.
Never did a Regiment perform harder and better service than this little band of Veterans. In the Battle of the 22nd of July, 1864, before Atlanta, Ga, they had the honor, with others, after desperate fighting, of capturing the celebrated DeGress Battery of 6, 12 pounders. The Brigade of the 16th Corps assisting in its recapture was the one to which the Western Sharpshooters was attached; but, after the Atlanta Campaign was attached to the 15th Corps and remained so until their muster out.
The Brigade after repulsing the charge on the left, was double-quicked some 3 miles toward the right of the railroad. The Brigade was formed with the 66th Illinois Sharpshooters on the right. The 66th came up at the Battery behind the works. Captain W.S. Boyd inserted the shell in a gun that burst. It was a percussion and not a fuse shell. The breech went 20 to 25 feet to the rear, The right trunnion went to the right over the breastworks, the left over the right wheel. The gun broke forward of the trunnions, turning end for end, the muzzle pointing inward, the shell remaining in the muzzle. It was said to be a miracle that none were killed or crippled by it. Just after this, some of De Gree's men put in an appearance and one of them told them that the gun had formerly been used with reduced charges on account of a flaw having been discovered in the piece.
The Division to which this Regiment belonged, being attached to the 15th Corps, marched with it on the ever-to-be-remembered campaigns of Georgia and South Carolina. On the Ogeechee River near Savanah, the Regiment being thrown to the front, on the 9th of December 1864, captured the Southern works protecting the Gulf Railroad, with a fine Blakely gun. At Savannah they were awarded the honor of being quartered in the old United States Barracks and were used for special duties.
Their last engagement was at Bentonville, NC, the 21st of March 1865. During their 3 years and 10 months of service the Regiment marched 5,000 miles, fought in 16 pitched battles and lost as many men in killed, wounded and disabled as they had when they mustered out of service on July 7, 1865.
| Total enrollment | 197 men |
| Killed in action | 17 men |
| Died of wounds | 2 men |
| Died of Disease | 17 men |
| Discharged for disability | 40 men |
| Total casualty rate | 38.5% |