The 110-acre (45 ha) district encompasses 35 buildings and two other structures (including the South Norwalk Railroad Bridge).

Half (5.5 acres (2.2 ha)) of the area first became part of the National Register of Historic Places in 1977 (35 buildings and two structures).

The district was first increased to add 9 contributing buildings over a 2.5-acre (1.0 ha) area.

The second increase added 10 contributing buildings over a 3-acre (1.2 ha) area.

[1] The district is a densely packed area, with an 1895 railroad bridge at its "visual center".