South Station Tower No. 1 & Interlocking System, Dewey Square, Boston, Suffolk County, MA

Significance: South Station's interlocking system was a prototypical solution to the problem of handling the huge numbers of track and signal changes required at a large railroad terminal. The interlocking system, Tower 1, and its electro-pneumatic interlocking machine were important elements in the design and historical operation of South Station, which was America's largest and busiest railroad station for many years.
Survey number: HAER MA-58
Building/structure dates: 1897- 1899 Initial Construction
Building/structure dates: 1939 Subsequent Work
Building/structure dates: 1959 Subsequent Work
Building/structure dates: ca. 1970 Subsequent Work
Building/structure dates: ca. 1977 Subsequent Work
Building/structure dates: ca. 1977 Subsequent Work