Concrete

When this 1,850-foot concrete-arch highway bridge was built on the White River in a remote region of northern Arkansas - prior to the construction of upriver, flood-control dams - flash floods occurred frequently, sometimes causing the water to rise as much as one foot per hour. Construction under these conditions presented a clear danger, so project managers specified both a design and an innovative construction method appropriate to the problem of building across a perilous stretch of unpredictable river.

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.

Upon its dedication in 1885, the Washington Monument was the tallest structure in the world. Begun in 1848 to honor George Washington, the structure wasn't completed for over 36 years. Construction and financing problems slowed progress and the Civil War halted it completely.

This majestic viaduct was built during the golden age of railroading. It was at the western end of a major readjustment in grade and alignment of the Erie-Lackawanna Railroad, and had double tracks to carry the trains across the valley of Tunkhannock Creek. The Hallstead cutoff (between Scranton, Pennsylvania and Hallstead, New Jersey) reduced passenger travel time by 20 minutes, and freight travel time by over an hour.

The Salginatobel Bridge, spanning the Salgina Valley ravine, is the earliest surviving three-hinged, hollow box arch bridge designed by  Robert Maillart.

The third bridge built on the same site to carry railroad tracks across the Susquehanna River just north of Harrisburg, Pennsylvania, the Rockville Stone Arch Bridge, at 3,820 feet long and 52 feet wide, is believed to be the longest and widest stone-arch railroad bridge in the world. A central link in rail travel between New York City and Pittsburgh, the Rockville Stone Arch Bridge accommodates four lines of railroad tracks, today serving both the Norfolk Southern and Amtrak lines.

No image dominates the Midwestern landscape like the monolithic grain elevator, whose present shape and construction owe much to grain company operator Frank Peavy and architect-builder Charles Haglin.

Wanting to improve on the flammability and cost of traditional wood-cribbed construction, Peavy speculated that reinforced concrete, in its infancy at the turn of the century, would outperform other materials. But critics feared that the elevator would collapse due to the vacuum created when grain was emptied from the air-tight structure.

The Rogue River Bridge was the most advanced concrete bridge in America when it was built. Distinguished bridge engineer Conde McCullough employed the techniques of Frenchman Eugene Freyssinet to create thin, graceful concrete arches for this seven-span structure.

Pre-compression of the concrete arch was achieved and, as a result of its success, pre-stressing became one of the hallmarks of American bridge building techniques.

The 16-story Ingalls Building, still in use today, was the world's first reinforced concrete skyscraper. Its success led to the acceptance of high-rise concrete construction in the United States.

Melville E. Ingalls, for whom the building is named, spent two years convincing city officials to issue a building permit. Skepticism was high, because the existing height record for a concrete building was only six stories.

Galveston Island is a barrier island located two miles off the Texas coast. The island is about 3 miles wide at its widest and about 28 miles long. The Galveston Seawall extends over 10 miles along Galveston's oceanfront, protecting life and property against hurricanes and tropical storms.