An amendment to the original charter was passed by the General Assembly in 1861, increasing the strength of the Company from sixty to one hundred and twenty enlisted men, with one major, one captain, four lieutenants, eight sergeants and eight corporals completing the roster of officers and non-commissioned officers where there had been but one captain, two lieutenants, three sergeants and four corporals under the first charter.

While the company of Horse Guards took no active part as a unit in the War of 1812, the Mexican War, the Civil War and the Spanish-American War, men from the organization had left the Company to take important parts in all four conflicts.

A second amendment to the charter, approved June 17, 1901, provided that upon application "either or both companies of the Governor's Horse Guards" could be organized as a troop of cavalry in the Connecticut National Guard with a personnel of "one captain, one first lieutenant, one second lieutenant, one first sergeant, one quartermaster sergeant, six sergeants, six corporals, two farriers, one saddler, two trumpeters and not more than forty nor less than thirty-five privates." Seeing in this act an opportunity to become a military unit, the organization promptly presented a petition, and an order was issued by Adjutant General Cole July 5, 1901, authorizing the immediate formation of the troop, to be designated as Troop "A," Connecticut National Guard. This was followed by the election of Luzerne C. Ludington to the office of captain of the Troop. William J. Bradnack was chosen first lieutenant and Robert J. Woodruff second lieutenant, with John Hugo first sergeant and the following members:—

Shortly after receiving recognition as a militia unit, the Troop was called together and it was decided that the Second Regiment armory on Meadow Street was unfitted for cavalry drill, so a committee was appointed to obtain a site for a new armory. Generous contributions on the part of prominent citizens enabled the erection of a wooden structure on the lot at 839 Orange Street. This building was barely completed when, in January 1905, it was burned to the ground.

Undaunted by this reverse, it was immediately decided to rebuild, and plans were made to put up a fire-proof structure. Once more men interested in the success of the Troop aided the building project by purchasing bonds, and the armory as it now stands was opened with appropriate ceremony in the Spring of 1906.

When the State bought the armory from the Troop it was suggested to men who held bonds covering the indebtedness on the building that the Troop should own a certain number of horses. Release from the payment of many obligations allowed the purchase of twenty horses in the Fall of 1909, and these were installed in the stables in the rear of the armory.

Funds to furnish the club rooms and pay interest on the building bonds were obtained through the willingness of the men to turn into the treasury the pay they received for the time spent in camp each year with the other militia units. These were added to from time to time by receipts from very popular and successful horse shows held in the winters of 1907, 1908, 1909 and 1910. These shows attracted exhibits from the best known fanciers in the East, and were famed as society events. Features of these shows were the crack drill exhibitions given by squads selected from the Troop's best riders. A military tournament, which included all competition that could be arranged for mounted men, followed when horse shows reached the point of exclusiveness they attained as the automobile came into common use.

During this period the men were being perfected in field work by road marches and manœuvers. In many of these they were placed under the command of regular army officers and rode beside troopers from the regular army, with due credit to their militia training.

In 1909 Sergeant Harry Denton was detailed by the War Department to instruct the Troop in the arts of war. The coming of this excellent soldier marked the advent of a new era for the unit. Riding classes were organized for ladies and large squads turned out every week for "monkey drill." Monkey drill taught the men the rudiments of trick riding and many of them became very well versed in handling their mounts and themselves in the difficult manœuvers. One of the best squads developed in the Troop included George Condren and John Paton, who later commanded the Company in France, Frank E. Wolf, who led the Company to its training area on the other side, George Wallace and Harold W. Herrick, who were commissioned officers during the great War, and others who were prominent in home activities during the period of hostilities.