Other members of "The Cyclone" were John Riggin, Wm. Charles and Orvill Mathews (the latter the late Commodore Mathews of the U.S. Navy), John Prather, Fred Benton, (later captain under Gen. Custer), Mr. Fullerton, (later a General, U.S.A.), Mr. Alfred Berenda and his brother, Mr. Ferd Garesche, Mr. Charles Kearney (son of Gen. Kearney), Mr. Edward Bredell, Jr., and a number of other young men of St. Louis.
Several of these men can be identified in Kennedy's 1860 St. Louis City Directory. Most interestingly, Edward Bredell, Jr. was the son of Edward Bredell, Sr., who was the president of the Missouri Glass Company. Bredell, Jr. worked for his father's company as a clerk, as did Merritt Griswold. Therefore, Bredell, Jr. and Griswold were not only members of the same baseball club but also co-workers.
According to Kennedy's Directory, John Riggin, Jr. worked for a real estate firm with his father, John Riggin, Sr. John G. Prather was employed with Daniel G. Taylor & Co., which sold wine and liquor. Ferdinand Garesche was a principle (along with John P. Norris) in the firm of Norris & Garesche who are listed as proprietors of the Western Spice Mills.
If one reads "Wm. Charles and Orvill Mathews" to mean "Wm. Charles Mathews and Orvill Mathews" then we can identify William Mathews, proprietor of Wm. Mathews & Co., as a member of the Cyclone Club. He is listed in the Directory as a commission merchant. There is no William Charles listed in the directory.
Fred Benton is Frederick William Benteen, who is listed in Kennedy's Directory as a painter. According to the Wyoming Tales and Trails website, Benteen was born in 1834, died in 1898, and retired from the United States Army as a brigadier general. It goes on to say that "At the beginning of the Civil War his family was living in St. Louis. As a result of the War, he was estranged from his father. At the beginning of the War, he announced his intention to enlist in Union forces. His father declared that he hoped his son would be killed by a Confederate bullet, preferable fired by a Benteen. Nevertheless, he enlisted. During the war he was responsible for the capture of a Confederate steamboat upon which his father was serving as an engineer. While other members of the crew were paroled, the elder Benteen remained imprisoned...His army career effectively ended upon a court martial for alleged drunkedness in which he was found guilty of three counts. Benteen, himself, felt himself a failure. " At the Battle of Little Big Horn, Benteen was in command of three companies and was wounded in the right hand.
Charles Kearny is listed in Kennedy's Directory as a clerk and according to the Encyclopedia of the History of Missouri was the son of Gen. Stephen Watts Kearny and the husband of Annie Stewart.
Orvill Mathews is, of course, Edmund Orville Matthews and Mr. Fullerton is J.S. Fullerton.
Based on this research, I have to seriously back away from the ideas that I had concerning the influence of St. Louis' military community on the development of baseball in the city. Certainly Orville Matthews was an active duty naval officer at the time he was a member of the Cyclone Club and Jeremiah Fruin was in the army when he came to St. Louis. Benteen and Fullerton, however, did not join the army until the Civil War and there is no evidence, so far, of Kearny serving in the military.
Update: Griswold, in his letter to Spink, also mentioned a "Mr. Whitney" who worked for "Boatman's Savings Bank" and was the one who suggested the name "Cyclone" for the club. "Mr. Whitney" was Robert S. Whitney who worked as a teller at what was then called Boatman's Savings Institution.