This is a list of open questions that I have found in my transit research. They vary greatly: some are attempting to narrow down to a month or day; others have a possible range of years. Some may be answered with a single dated source; others are probably just the tip of the iceberg. Any clues to these, even anecdotal, are welcomed.

MBTA Commuter Rail

Newburyport/Rockport Line

• When during the 1980s did most stations become accessible?
• When was West Beach replaced with Beverly Farms? (circa 1879)
• When exactly around 1852-55 was Beverly Depot relocated? Was the station moved?

Haverhill Line

• When was Haverhill station made accessible? (circa 2000)
• When were Bradford, Lawrence, Andover, and Ballardvale finished? When was Reading? (early 90s) How was Lawrence accessible?
• When in June 1976 was the final Haverhill trip? Did Ballardvale and Shawsheen last until April 1976? Yes

Lowell Line

• When exactly did Milk Row open? (tertiary sources variously say 1835 and 1842; more likely late 1840s)
• When did Gilman Square (February 19, 1937) and Somerville Junction close? (1940s)
• When precisely did East Cambridge and Prospect Hill close - upon state ruling, with Fitchburg Cutoff in April, or with High Line in May?
• When did Lechmere Warehouse open and close? (1979 and 1997?)
• When was North Billerica made accessible? (1998?)
• When was Mishawum originally closed? (between 1946 and 1952) When was it made un-accessible? (circa 2007)
• When was Lowell Union Station demolished?

Fitchburg Line

• How long was Silver Hill closure in 1981?
• When was West Concord made accessible? (circa 1991)
• When was Brandeis made accessible? (circa 1991?)
• What dates were Shirley station opened (May 1981) and rebuilt (1993)?
• When was Boxboro closed? (between 1946 and 1950)
• When was Willows closed (between 1917 and 1929)
• When was Wellington Hill opened? What was the platform/track configuration after the 1908 elevation?

Franklin Line

• How long was Plimptonville closure in 1981?
• Did Joseph N. Welch actually use Plimptonville?
• When were Norwood stations and Norfolk made accessible? (early 90s)
• When was Foxboro made accessible? (by 1996)

Providence/Stoughton Line

• South Attleboro: June 20 or July 30 opening? Very likely the latter. Definitely the latter.
• When was Hyde Park station built (~1913) and demolished (1970s?) When was it made accessible?
• When was Hebronville closed?
• What date in November 1977 was East Foxboro closed?
• When was Canton Junction moved? When were overpass and mini-highs added?
• When were Canton Center, Stoughton, and Mansfield made accessible? (1980s)
• What happened to the North Attleboro Branch streetcar line (Gee Whiz Line) after Attleboro was rebuilt in 1906?
• When did Attleboro renovations finish?
• When did Roxbury Crossing and Heath Street close? (prior to 1940)

Worcester Line

• When was Mill Dam/Brookline Junction replaced with Cottage Farm? (circa 1849-1857) Was it ever a stop again?
• Were Auburndale and West Newton fully closed in 1981? No, one daily round trip remained for each
• When was Framingham finished in 2001?
• When was West Natick made accessible? (circa 1993)
• Did Worcester originally have a mini-high, or was it a longer high from the start? A mini-high at the existing Amtrak station was built in 1994 for MBTA service. A 92-foot platform opened with the renovated Union Station in 2000; it was extended to 355 feet in 2001.

Others

• Was Back Bay only 2/3 accessible at first? No that was just an error in an MBTA document
• When did North Station and South Station accessibility finish? (circa 1991, circa 1989)
• When did Acushnet, Assonet, Crystal Springs close?
• Was there actually a Cottage Street station near Uphams Corner?
• Was Hersey accessibility delayed until the early 1990s?
• When did Ferry Street station reopen after 1940?

Green Line

Subway

• Was all Lechmere service moved to Kenmore in 1923, or did some Pleasant Street service remain?
• Was Symphony closed on Sundays in 1981? How long?
• When did Prudential renovation finish?
• When were elevators added to North Station elevated?

A Branch

• What were A Branch stops - particularly those on Brighton? (Definitely Linden and Harvard; probably Allston, St. Lukes, and Chester too.)
• When did through service from Watertown happen? (circa 1912?)

B Branch

• When exactly did the Kenmore-Packards Corner and Packards-Union segments open? (May 18, 1896 - but was part open before?)
• When was University Road closed? (circa 1975?)
• When was Alcorn moved to Babock? (circa 1975?)
• When were BU East, BU Central (and others?) rebuilt? Circa 1975?
• When were Leamington and Colbourne consolidated into Sutherland? (almost certainly 1980, but citation needed)
• When was BC accessibility work started/finished?

C Branch

• Did horsecar service ever run west of Coolidge Corner, or did service begin with electrification?
• When were Strathmore, Winthrop, and Carlton eliminated, and Summit/Winchester combined? (almost certainly 1982, but citation needed)
• When was St Marys, Washington Square, and Cleveland Circle accessibility work finished?

D Branch

• When did rebuilt Riverside station open? (between 1995 and 2000)
• When were stops initially made accessible?
• When precisely did Longwood and BV accessibility finish?

E Branch

• What years was Brookline Village-School Street segment operated as a horsecar line? Was there ever a short branch up Harvard Street?
• When did Cypress Street branch open? (circa 1888)
• What was the initial electrification pattern on Huntington - were all lines except Longwood on August 4, 1894? Was Brigham Circle - Roxbury Crossing also electrified then?
• When did Cypress Street carhouse open? (circa late 1894) November 1894 per Rollsign
• When was Longwood electrified? (circa late 1894) What were service patterns - was it later a shuttle?
• When did Forest Hills - Park Street via Columbus service end?
• When was Park-South Huntington-Forest Hills through service finally established? (After late 1915, possibly rather later)
• When did Brookline Village transfer station open? (circa 1912-1913)
• When did Forsyth, Parker, Vancouver, Wigglesworth close? When did Frawley? (probably all 1980, need citation)
• When did Back of the Hill open?
• When in 2003 did Brigham Circle accessibility finish?

MBTA subway etc

Transfer stations

• Did Temple Place entrance to DTX reopen for SL? Was it exit-only before? (Appears it was closed until 2002, then exit-only until around 2007, but needs more citations)
• When was Winter entrance to DTX reconfigured?
• What times was the Franklin Street entrance to DTX rebuilt? Was it exit-only for a while in the 80s?
• Which Park Street headhouses were exit-only, and when? When were they rebuilt?
• When was Winter Street Concourse work started/ended? (need citation mostly)
• Was Hawley escalator original to DTX?
• When did Haymarket and Park Street accessibility work finish?
• When did the renovated Haymarket entrance open in the Parcel 7 building? (circa 2000-2001)
• When did Exchange Building (53 State) entrance close? (maybe 1981)
• Was the City Hall entrance exit-only for a while in the 1980s?

Orange Line

• When did Assembly south headhouse open?
• When were the Hayward Place and Lagrange Place entrances to Chinatown station closed? (1972?) When was the Essex entrance closed? (1986?)
• What service patterns were operated on the Atlantic Avenue El (esp after 1928)?
• When did Community College, Sullivan, Wellington, Malden accessibility finish?

Blue Line

• Was Wood Island accessibility delayed?
• When did south exits (were they ever entrances?) to Maverick closed?
• When around 1990 was Wonderland finished? Ramps only?

Red Line

• When was Stadium station last used?
• What headhouses did Harvard station actually have? When were they closed?
• What changes to South Station and when?
• What changes to Fields Corner and when?
• When precisely did Fields Corner and Shawmut become accessible?
• How was Ashmont originally accessible?
• When did Quincy Center and North Quincy accessibility work finish?
• Were Braintree and Quincy Adams originally accessible, or was that added later?

MBTA Bus

• When did Lechmere-based bus routes switch to using only the O'Brien Highway busway? After the 2011 closure

Bay Area

BART

• When was Oakland West renamed as West Oakland? (1980s)
• When was Oakland City Center/12th Street renamed as 12th Street Oakland City Center? (circa 2005) Circa 2008, per maps and website
• When did Berkeley become Downtown Berkeley? (circa 1995?)
• When did Civic Center become Civic Center/UN Plaza? (circa 2005?)

Muni Metro

• When was 19th Street station in Dolores Park closed? (with LRVs?)
• When were M stops on 19th Ave closed? (With LRVs?) How many were there?
• What service patterns has the S Shuttle run, and when?