This area of "Wikipedia" contains much information on transit in Boston.
CITY TRANSIT HISTORY
1856-1887 - several companies
1887-1897 - West End Street Railway
1897-1947 - Boston Elevated Railway
1947-1964 - Metropolitan Transit Authority
Still has streetcars
1936-present - operated trolleybuses
HAS RAPID TRANSIT (opened 1897)
CURRENT TRANSIT SYSTEMS
Massachusetts Bay Transportation Authority
Serves Suffolk, Norfolk, portions of Middlesex, Essex, Plymouth Counties
Commuter service (various counties)
Bloom Bus Lines
Cavalier Coach
C&J Trailways
Coach Co.
Concord Coach Lines
DATTCO
Peter Pan Bus Lines
Plymouth & Brockton Street Railway Co.
Yankee Lines
OUTLYING TRANSIT HISTORY (CHELSEA)
1854-1880 - Boston & Chelsea Railroad
1880-1901 - Lynn & Boston Railroad Co.
1901-1911 - Boston & Northern Street Railway
1911-1919 - Bay State Street Railway Co.
1919-1936 - Eastern Massachusetts Street Railway
1936-1947 - Boston Elevated Railway
1947-1964 - Metropolitan Transit Authority
1952 - streetcars discontinued
1952-1961 - operated trolleybuses
OUTLYING TRANSIT HISTORY (LYNN)
1854-1901 - Lynn & Boston Railroad Co.
1901-1911 - Boston & Northern Street Railway
1911-1919 - Bay State Street Railway Co.
1919-1968 - Eastern Massachusetts Street Railway
1937 - streetcars discontinued
OUTLYING TRANSIT HISTORY (SALEM)
1875-1896 - Naumkeag Street Railway Co.
1896-1901 - Lynn & Boston Railroad Co.
1901-1911 - Boston & Northern Street Railway
1911-1919 - Bay State Street Railway Co.
1919-1968 - Eastern Massachusetts Street Railway
1937 - streetcars discontinued
OUTLYING TRANSIT HISTORY (MELROSE-WOBURN)
1892-1900 - Wakefield & Stoneham Street Railway
1900-1901 - Lynn & Boston Railroad Co.
1901-1911 - Boston & Northern Street Railway
1911-1919 - Bay State Street Railway Co.
1919-1968 - Eastern Massachusetts Street Railway
1946 - streetcars discontinued
OUTLYING TRANSIT HISTORY (QUINCY)
1888-1895 - Quincy Street Railway
1895-1899 - Quincy & Boston Street Railway
1899-1901 - Brockton Street Railway Co.
1901-1911 - Old Colony Street Railway Co.
1911-1919 - Bay State Street Railway Co.
1919-1968 - Eastern Massachusetts Street Railway
1948 - streetcars discontinued
OUTLYING TRANSIT HISTORY (HYDE PARK)
1889-1892 - Norfolk Street Railway
1892-1900 - Norfolk Suburban Street Railway
1900-1900 - West Roxbury & Roslindale Street Railway
1900-1911 - Old Colony Street Railway Co.
1911-1919 - Bay State Street Railway Co.
After 1919 - Eastern Massachusetts Street Railway
Streetcars discontinued
OUTLYING TRANSIT HISTORY (NEWTON/WALTHAM)
1868-1889 - Waltham & Newton Street Railway
1886-1901 - Newton Street Railway
1900-1907 - Waltham Street Railway
1901-1972 - Middlesex & Boston Street Railway
1931 - streetcars discontinued
OUTLYING TRANSIT HISTORY (NATICK)
1891-1893 - Natick Electric Street Railway
1893-1907 - South Middlesex Street Railway
1907-1972 - Middlesex & Boston Street Railway
1931 - streetcars discontinued
Dedham
CITY TRANSIT HISTORY
1921-1945 - Oakdale Community Garage Bus Line
1945-1950 - Boston Worcester & New York Street Railway Co.
1950-1958 - Dedham-Needham Transit Lines
1958-1967 - Transit Bus Line
1967-1972 - Middlesex & Boston Street Railway
1972-1974 - Massachusetts Bay Transportation Authority
CURRENT TRANSIT SYSTEMS
Dedham Bus
Serves portion of Norfolk County
Needham
CITY TRANSIT HISTORY
1919-1944 - Modern Bus Lines
1944-1950 - Boston Worcester & New York Street Railway Co.
1950-1958 - Dedham-Needham Transit Lines
1958-1976 - Needham Transit Co.
1976-1979 - Metropolitan Coach Service
1979-present - no transit service
CURRENT TRANSIT SYSTEMS
No city service
Weymouth
CITY TRANSIT HISTORY
1895-1899 - Braintree & Weymouth Street Railway
1899-1900 - South Shore & Boston Street Railway
1900-1911 - Old Colony Street Railway Co.
1911-1919 - Bay State Street Railway Co.
1919-1932 - Eastern Massachusetts Street Railway
1929 - streetcars discontinued
1932-1948 - Lovell Bus Lines
1948-1984 - Hudson Bus Lines
1984-1986 - Carey's Bus Lines
1986-1990 - Weybus
1990-present - no transit service
CURRENT TRANSIT SYSTEMS
No city service
Framingham
CITY TRANSIT HISTORY
1888-1903 - Framingham Union Street Railway Co.
1903-1927 - Boston & Worcester Street Railway Co.
1925 - streetcars discontinued
1927-1963 - Boston Worcester & New York Street Railway Co.
1963-1971 - Boston-Worcester Corp.
1971-1974 - Gray Line
1974-1979 - Wellesley Fells Bus Lines
1979-1984 - Suburban Lines
1984-2007 - LIFT (Local Inter Framingham Transit)
CURRENT TRANSIT SYSTEMS
MetroWest Regional Transit Authority
Serves portion of Middlesex County
Gloucester
CITY TRANSIT HISTORY
1886-1900 - Gloucester Street Railway
1900-1901 - Lynn & Boston Railroad Co.
1901-1911 - Boston & Northern Street Railway
1911-1919 - Bay State Street Railway Co.
1919-1921 - Eastern Massachusetts Street Railway
1921 - streetcars discontinued
1921-1966 - Gloucester Auto Bus Co.
1966-1967 - Cape Ann Transit
1968-1969 - McNiff-Dominick Transit Co.
1971-1974 - Community Bus Lines
CURRENT TRANSIT SYSTEMS
Cape Ann Transportation Authority
Serves portion of Essex County
Lawrence/Haverhill
CITY TRANSIT HISTORY (LAWRENCE)
Prior to 1893 - several companies
1893-1901 - Lowell Lawrence & Haverhill Street Railway
1901-1911 - Boston & Northern Street Railway
1911-1919 - Bay State Street Railway Co.
1919-1968 - Eastern Massachusetts Street Railway
1936 - streetcars discontinued
1968-1968 - Massachusetts Bay Transportation Authority (under contract)
1969-1974 - Trombly Motor Coach
CITY TRANSIT HISTORY (HAVERHILL)
Prior to 1893 - several companies
1893-1901 - Lowell Lawrence & Haverhill Street Railway
1901-1911 - Boston & Northern Street Railway
1911-1919 - Bay State Street Railway Co.
1919-1959 - Eastern Massachusetts Street Railway
1936 - streetcars discontinued
1959-1965 - Massachusetts Northeastern Transportation Co.
1965-1974 - Michaud Bus Lines
CURRENT TRANSIT SYSTEMS
Merrimac Valley Regional Transit Authority
Serves portion of Essex County
OUTLYING TRANSIT HISTORY (NEWBURYPORT/AMESBURY)
1902-1905 - Haverhill & Southern New Hampshire Street Railway (New Hampshire Traction Co.)
1905-1912 - Haverhill & Southern New Hampshire Street Railway (New Hampshire Electric Railways)
1912-1926 - Massachusetts Northeastern Street Railway (New Hampshire Electric Railways)
1926-1934 - Massachusetts Northeastern Street Railway (Associated Gas & Electric Co.)
1930 - streetcars discontinued
1934-1965 - Massachusetts Northeastern Transportation Co.
1965-1970 - Appleyard Bus Lines
1970-1974 - Michaud Bus Lines
Lowell
CITY TRANSIT HISTORY
1859-1900 - Lowell & Suburban Street Railway
1900-1901 - Lowell Lawrence & Haverhill Street Railway
1901-1911 - Boston & Northern Street Railway
1911-1919 - Bay State Street Railway Co.
1919-1968 - Eastern Massachusetts Street Railway
1935 - streetcars discontinued
1968-1975 - Massachusetts Bay Transportation Authority (under contract)
CURRENT TRANSIT SYSTEMS
Lowell Regional Transit Authority
Serves portion of Middlesex County
Brockton
CITY TRANSIT HISTORY
1891-1901 - Brockton Street Railway Co.
1901-1911 - Old Colony Street Railway Co.
1911-1919 - Bay State Street Railway Co.
1919-1968 - Eastern Massachusetts Street Railway
1937 - streetcars discontinued
1968-1969 - Massachusetts Bay Transportation Authority (under contract)
CURRENT TRANSIT SYSTEMS
Brockton Area Transit Authority
Serves portion of Plymouth County
(fixed route systems interconnect)
CITY TRANSIT HISTORY (NEW BEDFORD)
1872-1887 - New Bedford & Fairhaven Street Railway
1887-1974 - Union Street Railway Co.
1947 - streetcars discontinued
CITY TRANSIT HISTORY (FALL RIVER)
1880-1900 - Globe Street Railway
1900-1901 - Fall River Street Railway Co.
1901-1911 - Old Colony Street Railway Co.
1911-1919 - Bay State Street Railway Co.
1919-1965 - Eastern Massachusetts Street Railway
1936 - streetcars discontinued
1965-1969 - Short Line
After 1969 - Cozy Cab & Bus Co.
CURRENT TRANSIT SYSTEMS
Southeastern Regional Transit Authority
Serves Bristol County (part)
Attleboro/Taunton
CITY TRANSIT HISTORY (ATTLEBORO)
Streetcar co. - Attleboro North Attleboro & Wrentham Street Railway
Prior to 1895 - Interstate Consolidated Street Railway
1895-1933 - Interstate Street Railway Co.
1933 - streetcars discontinued
Private predecessor bus co. - Interstate Transit Co.
Period of no transit service
CITY TRANSIT HISTORY (TAUNTON)
1871-1901 - Taunton Street Railway
1901-1911 - Old Colony Street Railway Co.
1911-1919 - Bay State Street Railway Co.
1919-1960 - Eastern Massachusetts Street Railway
1932 - streetcars discontinued
After 1960 - Udna's
CURRENT TRANSIT SYSTEMS
Greater Attleboro Taunton Regional Transit Authority
Serves Bristol County (part), Plymouth County (part)
Bristol County is actually part of the Providence RI Metropolitan Area/transit systems connect in Providence
CITY TRANSIT HISTORY
1863-1907 - several companies
1907-1932 - Worcester Consolidated Street Railway (New England Investment & Security Co.)
1932-1952 - Worcester Street Railway Co.
1945 - streetcars discontinued
1952-1974 - Worcester Bus Co.
CURRENT TRANSIT SYSTEMS
Worcester Regional Transit Authority
Serves Worcester County (part)
OUTLYING TRANSIT HISTORY (CLINTON)
1893-1896 - Clinton Street Railway
1896-1901 - Leominster & Clinton Street Railway
After 1901 - Worcester Consolidated Street Railway
Streetcars discontinued
Private bus co. in 1952 - Rapid Transit Bus Lines
OUTLYING TRANSIT HISTORY (MILFORD)
Streetcar co. - Milford Street Railway
1896-1897 - Milford & Hopedale Street Railway Co.
1896-1902 - Milford Holliston & Framingham Street Railway Co.
1901-1928 - Milford & Uxbridge Street Railway
1928 - streetcars discontinued
Private bus co. in 1952 - North Milford Transportation Co.
OUTLYING TRANSIT HISTORY (LINWOOD)
After 1900 - Linwood Street Railway
Streetcars discontinued
Period of no transit service
Fitchburg/Leominster
CITY TRANSIT HISTORY
1886-1892 - Fitchburg Street Railway
1892-1978 - Fitchburg & Leominster Street Railway
1932 - streetcars discontinued
1932-1946 - operated trolleybuses
CURRENT TRANSIT SYSTEMS
Montachusett Regional Transit Authority
Serves Worcester County (part)
OUTLYING TRANSIT HISTORY (GARDNER)
1894-1899 - Gardner Electric Street Railway
1899-1913 - Gardner Westminster & Fitchburg Street Railway
1913-1924 - Northern Massachusetts Street Railway
1924 - streetcars discontinued
Private bus co. in 1952 - Flanagan's Bus Lines