"The engagements in December numbered only about eight and were geographically spotty, ..."
December 2 - 31, 1868: Rondout, New York; Newark, New Jersey; Norwich, New York; Scranton, Pennsylvania; Fort Plain, New York; Detroit, Michigan; Lansing, Michigan; Tecumseh, Michigan; Akron, Ohio;
December 2 - Clemens presumably caught the Hudson River Railroad’s 11:30 a.m. from New York, express to Albany and Troy, leaving the train en route to cross the Hudson River to Rondout. Lectured at Washington Hall, Rondout, New York
December 3-7 New York
December 8 Hartford
December 9: Depart Hartford 1:20 am for New York, Opera House, Newark, New Jersey
Returned to the Everett House in New York City at midnight. ...had to stand around the ferry house twenty minutes before I could get a carriage, & so got chilled through.
SLC to Jane Lampton Clemens and Family, 10 Dec 1868, New York, N.Y. (UCCL 02728), n. 1.
December 10 - Departed New York, spending that night at the Delavan House in Albany
December 11 - Norwich, New York Depart Norwich December 14 for New York City.
December 16 - Scranton, Pennsylvania. The librarian at Scranton Public Library has informed me that Twain's lecture took place at Washington Hall, a site noted for oratory in the 1860's.
December 17-18 in Elmira:
December 19. Fort Plain, New York – Sam was the guest of his poet-friend, George W. Elliott (1830-1898) and wife until December 21. One week after Clemens’s visit Elliott wrote this account of his arrival:
As the eastward bound express train halted at this station, in that glorious flood of sunlight of last Saturday afternoon, there stepped from the drawing-room car a little merry-eyed, curly-headed, intelligent-looking gentleman, whose age is hardly thirty-five. From one of his overcoat pockets peeped out a copy of Dickens’ “Old Curiosity Shop;” and from the other, as he walked along chatting with a friend, he drew and leisurely shelled and ate a handful of peanuts. This was Mr. Samuel L. Clemens, familiarly known to the reading public as “Mark Twain,” and acknowledged, wherever the English language is spoken, as par excellence the “Humorist of America.” With his calm self-possession and winning geniality of manner, added to a slight “Down East” accent, he is the impersonation of the shrewd, fun-loving, genuine “live Yankee.” . . .
We have an unwavering faith in “Mark Twain.” We count upon his success as confidently as upon the coming of an expected comet. (Elliott, 3)
SLC to Olivia L. Langdon, 19 and 20 Dec 1868, Fort Plain, N.Y. (UCCL 00206), n. 12.
There is no documentation that I've found but it seems very likely that Mark Twain spoke at the Diefendorf Hall in Fort Plain.
December 21: Arrive in Detroit
December 22 - Young Men's Hall, Detroit, Michigan
December 23 - Lansing, Michigan, College Hall, on what is now Michigan State University seems a likely site for Twain's lecture.
December 25: To Olivia L. Langdon 25 December 1868 • Lansing, Mich.
And now is the time to love—for on this day the Savior was born, whose measureless love unbarred the gates of Heaven to perishing men….I must to bed. I ride 20 miles in a cutter to-day, & lecture tonight at Charlotte.”
Clemens arrived and lectured in Charlotte on Christmas, leaving for Tecumseh, Michigan, the next day. It is possible he lectured at Sampson Hall, the location of which is unknown.
December 26 - Tecumseh, Michigan. The location of Twain's lecture has not been determined but is likely to have been within what is now Tecumseh's Downlown Historic District.
December 30 - Methodist Church, Akron, Ohio then returned to the Fairbanks home in Cleveland. The identity of this Methodist Church has not been determined but it is possible the he spoke at The Old Stone Church.