East Boston Streetcar Tunnel opens.

[12/20] Engineer: Carson, Howard A. It runs under Boston Harbor and connects downtown Boston to Boston. It is the second major underwater rail tunnel constructed in the U.S. (after one between Port Huron, Michigan and Sarnia, Ontario). (It is the largest and longest underwater rail tunnel in the world-Morgan). Some 32,000 people use the line on its first day. The line is extended to Scollay Square Under and Bowdoin Square on March 18, 1916, and is converted to a rapid transit line in 1924.*