MBTA Red Line's 100th anniversary
What's now the Orange Line, back then an elevated railway, was completed in 1901.
The East Boston Tunnel, the first major underwater rapid transit line in the country, began service in 1904.
These were all evolutionary surface systems, paving the way to the future. The Green and Blue lines used surface streetcars, while the Orange Line elevated had more efficient, faster multiple unit rapid transit trains.
-Bradley H. Clarke