Steel

The steel dome stretches 200 feet in diameter and rises 100 feet at its top. To accommodate thermal expansion, the inverted bowl-shaped structure originally rested on rollers that sat on the flat tops of six-story columns

There was a time when Americans from the Eastern seaboard braved long rail trips to southern Indiana in hopes that the water at the French Lick natural mineral springs could bring relief from alcoholism, pimples, gallstones and a host of other ailments and illnesses.

The Watertown Arsenal was the first major engineering testing laboratory in America. It was created to store and manufacture cutting-edge military technology and weaponry. The United States Army Research and Materials Laboratory continued to use the site until 1989, employing soldiers and civilians to produce and test artillery.

The bridge is 408 meters long and weighed approximately 1,500 metric tons when built. Originally supported by four columns, two more were added in later years to support the weight of heavier rail cars.

Three rivers - the Allegheny, Monongahela, and Ohio - join in Pittsburgh, making the city a natural site for the building of bridges. But the Smithfield Street Bridge stands apart from other Pittsburgh bridges for several reasons: it replaced structures by two well-known bridge engineers, Lewis Wernwag and John A. Roebling; it was the first use in America of the lenticular - or lens-shaped - truss design; and it was one of the first major bridges in the U.S. built primarily with steel.

The Fort Peck Dam was a cornerstone project of the Works Progress Administration of Franklin D. Roosevelt's New Deal. It required the largest construction plant and workforce since the construction of the Panama Canal and peaked at 11,000 workers. It was the largest dam of any type in the world for over 30 years.

"An essential part of the human experience is to create an aesthetic atmosphere."

The George Washington Bridge represented a departure in suspension bridge design. Chief Engineer O.H. Ammann developed a system of stiffening trusses that offered greater flexibility and saved the project nearly $10 million. Initially, just six of the upper eight lanes were paved, but Ammann designed the bridge to easily accommodate a future lower level.

Swiss-born O.H. Ammann (1879-1965) was Chief Engineer for the Port Authority of New York and New Jersey during the bridge's construction.