Massachusetts Avenue extends over 16 miles through 10 towns, and serves as a major thoroughfare for Dorchester, the South End, Arlington, and several squares in Cambridge.
It also played a major role in the Revolutionary War — Paul Revere, Samuel Dawes, and William Prescott rode along the avenue to Lexington and Concord on April 18, 1775 in their famous "midnight ride".
(At the time, the Mass Ave Bridge had not been constructed. Revere had to covertly row across the Charles River to reach Charlestown.)
Several years after the Mass Ave Bridge (real name: the Harvard Bridge) was completed in 1891, Harry Houdini jumped from it, shackled, into the Charles, before managing an underwater escape. Yes, there are pictures.