1860-1869

The Ashuelot Covered Bridge is located at the center of Ashuelot, NH. It is a Town lattice truss bridge, spanning the Ashuelot River in a roughly north-south orientation. It consists of two spans with a total length of 178 feet (54 m). The total width of the bridge is 29 feet (8.8 m), and has a central roadway and sidewalks (measuring 3'10" in width) on each side. The bridge rests on stone abutments and a central pier. The abutments have been reinforced with concrete since the bridge was built, and the central pier has been protected by a metal breakwater.

In the context of naval warfare, H.L. Hunley changed the world.  Its builders' innovative use of materials, design and manufacturing techniques resulted in the world's first successful attack submarine.

Most great monuments of nineteenth-century American engineering, such as the Brooklyn Bridge, dominate the surrounding landscape. By contrast, the Hoosac Tunnel, dug through a mountain in western Massachusetts, is inconspicuous, as tunnels naturally are. Yet it stands in the front rank of the projects of its age by whatever standards of measurement one chooses. On the one hand, its construction, which began in 1851 and ended in 1875, took almost two hundred lives, damaged many reputations, and nearly claimed the solvency of the commonwealth of Massachusetts.

"May God continue the unity of our Country as this Railroad unites the two great Oceans of the world."  
- Inscription on the ceremonial Golden Spike 

The symbolic Golden Spike, staked in Promontory, Utah in 1869, marked the completion of the first transcontinental railroad, joining the Union Pacific Railroad from the East and the Central Pacific Railroad from the west. 

Constructed to provide a safe, potable water supply for the citizens of Chicago, Ellis Chesbrough's Chicago Water Supply System was the first major system to utilize offshore intake systems. The system includes the landmark Chicago Water Tower and the Chicago Avenue Pumping Station. Its subaqueous tunnel was a pioneering effort in American civil engineering.

The Watkins Woolen Mill is among the best preserved examples of a Midwest woolen mill in nineteenth-century United States. Its machinery for preparing, spinning, and weaving wool reflects the existence of well-established textile industry in the country. It was designed and built by Waltus L. Watkins (1806-1884), a machinist and master weaver from Frankfort, Kentucky, who began operating his mill in 1861 in Clay County.

The Cairo is the sole survivor of the fleet of river gunboats built by the Union during the Civil War with the object of controlling the lower Mississippi River. Designed by Samuel Pook and built by James B. Eads, it saw limited battle and was sunk on the Yazoo River in 1862 by newly developed electronically detonated mines, becoming the first craft ever sunk by this predecessor to torpedo technology. The 175-foot ironclad vessel had 13 guns.

The design of the Bollman Truss Bridge-patented in 1852 and one of the first to use iron exclusively in all essential structural elements-was critical in the rapid expansion of American railroads in the 19th century. Replacing wooden bridges, which  were cumbersome to build and vulnerable to decay, the Bollman Truss Bridge could be built relatively quickly and inexpensively, while providing the long-lasting qualities associated with metal. This allowed new rail lines to be built over long distances in a short period of time.

Central Pacific Railroad served as the Western terminus of America's first transcontinental railroad, passing through the formidable Sierra Nevada Mountains. In all, 15 tunnels were blasted through solid granite. 

Thousands of Chinese from Kwantung Province were recruited by Central Pacific Railroad Company and became known for their diligence and hard work. In the second year of construction, nine out of ten workers on the CPRR were Chinese.