While researching Civil War ancestors I encountered the Military Order of the Loyal Legion of the United States.
Wikipedia describes this organization as the following :
The Military Order of the Loyal Legion of the United States, also known by its acronym MOLLUS or simply as the Loyal Legion, is a United States patriotic order, organized April 15, 1865, by officers of the Army, Navy, or Marine Corps of the United States who "had aided in maintaining the honor, integrity, and supremacy of the national movement" during the American Civil War. They stated as their purpose the cherishing the memories and associations of the war waged in defense of the unity and indivisibility of the Republic; the strengthening of the ties of fraternal fellowship and sympathy formed by companionship in arms; the relief of the widows and children of dead companions of the order; and the advancement of the general welfare of the soldiers and sailors of the United States. The modern organization is generally composed of descendants of these officers (hereditary members), and non-officer descendants who share the ideals of the Order (associate members).
Following the assassination of President Abraham Lincoln in 1865, rumors spread that the act had been part of a wider conspiracy to overthrow the legally constituted government of the United States by assassinating its chief men. Many people at first gave credence to these rumors, including three of the officers assigned to the honor guard for Lincoln's body as it was transported to Springfield, Illinois, for burial. The three officers, Brevet Lt. Col. Samuel Brown Wylie Mitchell, Lt. Col. Thoms Ellwood Zell, and Capt. Peter Dirk Keyser, are considered to be the founders of the Order. To demonstrate their loyalty, they decided to form a "Legion" modeled on the post-Revolutionary War Society of the Cincinnati. The Legion was organized largely during the same meetings that planned Lincoln's funeral, culminating in a meeting on May 31, 1865, in Philadelphia's Independence Hall at which the name was chosen, and a mass meeting of Philadelphia war veterans on April 20.
Further reading about MOLLUS :
Finally a listing of titles from Archive.org - Military Order of the Loyal Legion of the United States - here can be found member registers for various states.