USA

Designed and constructed in the early 1940s, this laboratory has an unequalled capacity to simulate a wide range of climatic conditions from arctic cold to jungle moisture. Data from tests of some three hundred different aircraft and over two thousand items of equipment has provided information vital to the performance, safety, and reliability of aircraft operating in extremes of weather.

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 granite milestones marking the Mason-Dixon Line bear crests from the two parties involved in the land-grant dispute, the families of William Penn and Charles Calvert (also known as Lord Baltimore). 

Designed by Claude A. P. Turner, a pioneer of reinforced concrete construction, the Marshall Building was constructed originally in 1906 as a five-story building. In 1911 the sixth floor of the building was added as per Turner's original design. This building is the oldest extant example of Turner's "mushroom" flat-slab system which transformed the design and construction of reinforced-concrete floors worldwide.

When opened in 1909, the 1,470 foot long main span of the Manhattan Bridge was the third longest suspension bridge span in the world, after the nearby Brooklyn and Williamsburg Bridges. The Manhattan Bridge has two 725 foot long suspended side spans for an overall length of 2,920 feet. The bridge deck is supported by 4 main cables of 20.75 inch diameter, each composed of more than 35,000 individual wires. The bridge deck is stiffened by four parallel trusses of 24 foot depth, hinged at the towers.

The Mackinac (pronounced "Mack-in-awe") Bridge (1957) spans the Straits of Mackinac between Lake Michigan and Lake Huron, connecting the Lower and Upper peninsulas of Michigan.   Prior to the construction of the bridge, a fleet of nine ferries would carry as many as 9,000 vehicles per day, with traffic backups stretching as long as 16 miles.

At the mountain where the Civil War's Battle Above the Clouds was waged, tourist business has thrived from the building of its first toll road (Whiteside Pike) in 1857 to present day.