The Sons of Veterans Reserve (SVR), originally formed as the GAR's "Corps of Cadets," was an auxiliary of the GAR comprised of the Union Veterans' sons and grandsons. The SVR functioned as a uniformed and ceremonial component of the GAR as well as serving as the local militia. 

In 1881, the GAR authorized the creation of a Corps of Cadets, founded by Major Augusts P. Davis. The Corps was composed of sons and grandsons of Union veterans. This organization evolved into the Sons of Veterans Reserve (SVR). 

Major Davis' vision for the organization: 

"The Sons of Veterans is destined to become the great military organization of the country, that glory of its supremacy, that healing of the sense when its National hymn are sung that none other not thus reared can know or feel. Through this organization the declining days of the Union Veteran will be made pleasant, his record of service to his country preserved, his memory honored, patriotism promoted. While if the dire necessity of the Nation should dictate, the Sons of Veterans, uniformed, drilled and equipped would come at once to her defense with the glory of their fathers surrounding them, each heart pulsating in unison with the rising and falling of the Nation's emblem. And who would be powerful enough to prevail against such a host?" 

By 1884 the Corps of Cadets (now named the Sons of Veterans) membership grew to over 20,000. By 1890 the organization swelled to over 145,000 members. 

In 1903 the Sons of Veterans split into two different organizations with two different mission statements. Now called the Sons of Veterans Reserve continued the military tradition, while the new Sons of veterans of the USA (renamed the Sons of Union Veterans of the Civil War in 1925) would follow a more patriotic and educational path. 

The largest, best equipped, and most disciplined brigade in the entire SVR was the Pennsylvania Brigade. The Blues once belonged to this brigade. By 1914, the Pennsylvania Brigade included:

• 197 officers

• 4,997 enlisted men

• Four infantry regiments

• Five cavalry troops

• Two artillery batteries

• A fully staffed field hospital

SVR units were considered part of the militia system and many of the local SVR units (including the Blues) were adopted by the early National Guard system and was treated as an auxiliary unit. Members drilled twice monthly and were armed with .45‑70 Trapdoor Springfield rifles.

During the Spanish American War, the country called for volunteers. Several SVR units, including the Blues, volunteered for federal service. SVR units were activated at the state and federal level. The SVR units fought alongside US Regulars, National Guard units, and other strictly volunteer units. After the Spanish American War the SVR sought federal recognition as an official reserve component of the United States Army. However, the bill was never passed. 

During World War I, the Blues and other elements of the Pennsylvania Brigade were federalized and attached to the 108th and 109th Infantry Regiments of the 28th Division.

After WWI the current National Guard system no longer considered the SVR an active reserve component of the United States Army. However, President Warren G. Harding (a member of the Sons of Union Veterans of the Civil War) armed the SVR with surplus rifles.