Exhibition Theme: Technology

• Boston

Marble Architecture

• Technology

• Boston

Cotton and Wool Mills

• Technology

• Philadelphia

Prisons

• Technology

• Philadelphia

United States Mint

• Technology

• Philadelphia

Iron and Steel Manufacturing

• Technology

• Washington D.C.

Printing Office

• Technology

• Washington D.C.

Postal Service Headquarters

• Technology

• Washington D.C.

National Observatory in Georgetown

• Technology

• Washington D.C.

Streetcars

• Technology

• New York

Ferries and Piers

• Technology