The inquirer here may have been Richard Dennis Steuart (1878-1951) of Baltimore (see 'CV': Vol. 24, @ p. 142).
It appears he may have been inquiring about L-Col. Samuel R. Harrison, 1 LA Infantry. (L-C Harrison apparently resigned from this unit in Jun., '62).
Given the inquiry at first instance was for Col. Samuel T. Harrison (not Col. Samuel R. Harrison), the inquirer may not have been well acquainted with the gentleman he was inquiring about. Thought he might have made the acquaintance of this Confederate veteran following the war, or he may have heard about him through someone else, say a relative. (It seems he did not know the targeted person very well, as he got the middle initial wrong in his initial inquiry).
Interestingly, there is a 'Find-a-Grave' listing (see below) for a Col. Samuel R. Harrison (c.1804-1863), who is buried in a Maryland Cemetery.
But cannot determine the reliability of the information in this listing nor establish a connection between this person buried and the one who is the subject of the inquiry.
I was wondering about the printed Header of the letter. Did the Confederate Veteran represent the UDC? Did the UDC contribute to the publication of the magazine back in those days?
Pursuant to the undertaking given by the 'Confederate Veteran' in their displayed letter dated Feb. 10, 1916, they published the inquiry made by Mr. Steuart in the subsequent March 1916 edition of the 'Confederate Veteran' (CV) magazine.
The full notation of the reference previously cited is:-
'Confederate Veteran' (CV) magazine, Volume 24, at page 142 (on the viewer).
Description based on: v. 2, no. 1 (Jan. 1894); title from cover
archive.org
The relevant published extract reads:-
...'R. D. Steuart, 1103 Edmondson Avenue, Baltimore, Md., wants some information of Lieut. Col. Samuel T. Harison (or Harrison). He wants to know his command and something about him.'...