March 23 Saturday – Alta California printed Sam’s article “KEY WEST” dated Jan. 6 [Schmidt].
Camfield lists this as “Letter from Mark Twain” Number VII [bibliog.].

March 19 Tuesday – Sam wrote from St. Louis to Charles Webb asking Webb to telegraph the expected publishing date of the Jumping Frog book, saying that if it is more than ten days off, “I had better lecture here.” Sam felt he would have to return to New York if the book was to be out soon. Webb answered that he could not have the book out before April 25 [MTL 2: 18; Sanborn 323]. Note:
The book was not published until about May 1 and never sold well. Webb simply didn’t have “the stuff” to market Sam properly.

March 17 Sunday – Sam was asked to make a few remarks to a Sunday school, at his sister Pamela’s church. Sam told the “Jumping Frog” story, but could not supply a moral from the story, so “let it slide” [MTL 2: 19 n2; Sanborn 322].
Alta California printed Sam’s article “UNDER WAY AGAIN” which Sam dated Jan. 1 [Schmidt].
Camfield lists this as “Letter from Mark Twain” Number VI [bibliog.]. Sam’s article “A Curtain Lecture Concerning Skating” ran in the New York Sunday Mercury [Camfield bibliog.].

March 16 Saturday – Alta California printed Sam’s article “THE TWIN MOUNTAINS” which Sam dated New Year’s Day [Schmidt]. 

Camfield lists this as “Letter from Mark Twain” Number V [bibliog.].

March 15 Friday – Alta California printed Sam’s article “THE FIRST DEATH” which Sam had dated from December 24 to January 1 [Schmidt]. 

Camfield lists this as “Letter from Mark Twain” Number IV [bibliog.]. Sam’s article “Iniquitous Crusade Against’ Man’s Regal Birthright Must Be Crushed” ran in the Missouri Democrat [Camfield bibliog.].

March 14 Thursday – The first of five letters from Hawaii, reprints of five early Sacramento Union letters with “a few minor omissions” ran in the New York Weekly. Dated Mar. 18, 1866, beginning: “We arrived here to-day at noon…” this first article omitted “the short anecdote of Brown’s mistaking a cake of soap for a ‘curious foreign dish’” [The Twainian, Mar. 1944 p2-3]. These letters are notable for their promotional value to Sam’s upcoming New York lecture.

March 13 Wednesday – Sam’s “Volley from the Down-Trodden” ran in the Missouri Democrat [Camfield bibliog.].

March 12, 13 and 15 Friday – Three articles: “Female Suffrage: Views of Mark Twain” first appeared in the St. Louis Missouri Democrat on these days [Budd, “Collected” 1007; MTTMB 287n1].
These were reprinted in the Alta California April 10, 28, and May 11. From two of Sam’s letters on suffrage:

March 7 Thursday – The New York Weekly announced it would print (re-print) a series of Mark Twain’s “inimitable papers.” The weekly reprinted five of Sandwich Islands Letters to the Union, but without mention of the prior publication [MTL 2: 12n3].

March 6 Wednesday – Artemus Ward (Charles Farrar Browne) died of tuberculosis after his last performance on Jan. 23 in London. Ward was 33. He was interred near London but his body was later shipped back to America to be buried at Waterford, Maine. It arrived in New York in May, when Sam noted the event in one of his Alta letters.