Mechanics Hall (Boston, Massachusetts) was a building and community institution on Huntington Avenue at West Newton Street, from 1881 to 1959. Commissioned by the Massachusetts Charitable Mechanic Association, it was built by the noted architect William Gibbons Preston. The building was located between the Boston and Albany railroad yards and Huntington avenue. It was razed for the Prudential Center urban renewal project of the early 1960s.

Mechanics Hall is a concert hall in Worcester, Massachusetts. It was built in 1857 in the Renaissance Revival style and restored in 1977. Built as part of the early nineteenth-century worker's improvement movement, it is now a concert and performing arts venue ranked as one of the top four concert halls in North America and in the top twelve between Europe and the Americas. It also houses a recording studio.

Wikipedia

For the first few decades of Indianapolis’ existence, regular theatrical entertainment wasn’t on the top of most Hoosiers’ priority lists.

Possibly misidentified, this location my actually be North Hall.  North Hall was constructed in 1865, to be used, in part, as a University Chapel. The original recommendation, made by Governor Samuel Kirkwood, requested funds for a chemistry laboratory, chapel and astronomical observatory, and over the years, North Hall, the two-and-a-half-story, red-brick classic, certainly became a multi-use facility.

Moravian University is a private university in Bethlehem, Pennsylvania. The institution traces its founding to 1742 by Moravians, descendants of followers of the Bohemian Reformation under John Amos Comenius.

The College of Music of Cincinnati was founded in 1878 by George Ward Nichols and funded with a lead donation from Reuben Springer. The famed conductor Theodore Thomas was immediately hired as the director, a fitting choice since Thomas had been informally involved in education all his life by bringing symphonic music to people throughout the United States. Initially classes were held in Dexter Hall, which was adjacent to the newly-constructed Music Hall.  

I have found no documentation indicating the name or location of Mark Twain's lecture in Galesburg.  Yet Galesburg does have an appropriate site:

William, who never actually lived in Decatur, was the first Powers to start building commercially. After purchasing farmland in rural Macon and McClean counties, in 1856 he turned his attention to the city, constructing a group of buildings in what became known as Powers Block — the south side of 100 block of East Main. Among those buildings was Powers Hall, which housed Decatur’s first auditorium.

Queen's Hall. First hall in Montreal expressly constructed for concert use. It was built in 1880 on the northwest corner of Ste-Catherine and Victoria streets. The auditorium seated 1159 and was equipped with an organ. It served as the home of the Montreal Philharmonic Society (1880-9) and the Mendelssohn Choir of Montreal (1881-90) and was the scene of Emma Albani's three recitals on her return to Canada in March 1883.

In 1935, the bowling and billiard hall that Erve managed was in the Hall-Rand building on the northwest corner of Congress and Third Streets in Troy. This was the former Rand’s Hall, later Rand’s Opera House, expanded in 1872 as a concert room, lecture hall and place of exhibitions. How Rand’s Hall became “Hall-Rand,” or how an opera house became a bowling alley, I don’t know. I also don’t know how “Erve” is pronounced. Sadly, it’s long gone, and a  former chain restaurant building housing a fast food buffet occupies what should be a prominent corner of the city.

The Colonial Revival-style City Hall of Waltham, designed by Kilham, Hopkins and Greeling, was built in 1926 and opened and dedicated in 1927. It stands on the old site of Rumford Hall, a building constructed a century earlier, in 1827, to house the Rumford Institute. Founded in 1826, the Institute was a lyceum, with lectures and classes in the arts and sciences for the female mill workers at the Boston Manufacturing Company, which built the Hall. An early instructor at the Institute was the Unitarian minister and educator, Bernard Whitman.

I have found no documentation linking Twain to this site but it does seem a good fit for his December 25, 1868 lecture:

SAMPSON HALL Size of stage 22 x24 Seating capacity 900 Eight sets of scenery Rent one night $15 two nights $25 three nights $30 one week $50 License 82 Will share with good attractions Address AH Sleater Manager or Homer Green Agent Seats sold at Western Union Telegraph Ofiice 

The plotted location is for the Eaton County Court House.  The actual location of Sampson Hall is unknown.

In 1864, William Steinway built elegant showrooms housing over 100 Steinway & Sons pianos at 109 East 14th Street, at the corner of Fourth Ave.

The four-story brick building fronts on Monroe at the SW corner of Justice, the portion of street visible at the left (now Ottawa Ave.) Signs on the front the the building advertise the various tenants such as "Foster Brothers, Great New York City Stores" and the "Commercial College." The street level shops display their wares on the sidewalk in front of the various businesses. Originally the fourth floor was used as an assembly hall. A horse and cart are on the far right and a gas street light is on the corner.

November 2, 1871 - Town Hall, Exeter, New Hampshire - "Artemus Ward"

EXETER'S HISTORIC TOWN HALL

February 18, 2015

Mark Twain and George W. Cable were indeed in Saratoga Springs on February 20, 1885. His lecture was part of a series sponsored by the Saratoga Athenaeum, a private subscription library that was founded in 1885. I believe this was the first lecture and have not been able to determine if there were others. 

Tweddle Hall was the pre-eminent concert venue in Albany on the corner of State St. and North Pearl St. for decades (a Citizen’s Bank is there today). It was mostly destroyed by fire in 1883, and then re-built as the Tweddle Building several years later, housing office and stores. (By now there were other concert venues.) The Tweddle Building was demolished circa 1912 to accomodate the expansion of the Ten Eyck Hotel, which was demolished circa 1970 for the bank,

Friends of Albany History

West side of Portage St. (2nd floor), south of E. Main St. (now E. Michigan Ave.).

Built as “Union Hall” and run as an opera house from 1866 to 1900. Renovated and renamed “Opera House” in 1881 in competition with the Academy of Music. Theater torn out and building converted to offices in 1900.

Kalamazoo Public Library

In 1871 the American Block was built, with its Union Hall at 9 East Main Street, billed as “the best public hall aside from the Opera House at Dunkirk.” It was a lavishly frescoed room with seating for 1,000, although the main entrance had to be altered in 1872 to eliminate drafts. The competition that Union Hall offered was too much, and at that point, the Concert Hall in the Center Block, in effect, went out of business and was sold to be remodeled as a Masonic lodge.

The point mapped is actually the address of Angell Hall. Angell Hall is an academic building at the University of Michigan in Ann Arbor. It was previously connected to the University Hall building, which was replaced by Mason Hall and Haven Hall. Angell Hall is named in honor of James Burrill Angell, who was the University's president from 1871-1909. http://en.wikipedia.org/wiki/Angell_Hall University Hall North wing (Mason Hall) built in 1840, South wing (South College) built in 1848, Central wing built in 1871.