USA

The Detroit-Windsor Tunnel is a 5,160-foot structure that carries traffic under the Detroit River between Detroit, Michigan and Ontario, Canada. Privately financed, built, and owned, it was completed in 26 months, 10 months ahead of schedule. 

The concept of heating a number of buildings in the core area of a city from a single heating plant was introduced into the United States by Birdsill Holly at Lockport, New York, in 1877. The gain in thermal efficiency of a single large steam plant over a series of small isolated boilers led to widespread commercial installation of district heating. Organized by the Detroit Edison Company, the Central Heating Company began service here in 1903, supplying twelve customers with steam piped from the Edison Company's Willis Avenue Plant. Today's greatly enlarged system continues in operation.

Delta Air Lines’ historic buildings consist of two aircraft hangers and several office buildings at the Delta World Headquarters site constructed between 1941 and 1947. On March 1, 1941, Delta Air Lines moved its corporate headquarters to Atlanta, constructing offices space and Hangar 1, the largest aircraft hangar in the Southeast United States at what was then Atlanta Municipal Airport. The airport was later renamed Hartsfield – Jackson International Airport in honor of Atlanta Mayors William B. Hartsfield and Maynard H. Jackson Jr.

The Delaware Aqueduct provided an important transportation link between the Pennsylvania's coalmines and New York's booming industrial marketplace. It is the earliest surviving work of John A. Roebling, who designed the Brooklyn Bridge  30 years later. The cable anchorage system first used on this project was also used on the Brooklyn Bridge. The aqueduct is patterned after Roebling's design of the Pennsylvania Canal over the Allegheny River, and is the oldest metal strand cable suspension bridge still standing in the U.S.

Before the Davis Island Lock & Dam were built, the flow of the Ohio River slowed to little more than a trickle during dry periods. For several months each year, the unreliable flow stranded Pittsburgh's steamboats, towboats, and barges.    

The Davis Island Lock & Chanoine Dam experimental project was the first lock and dam ever constructed on the Ohio River. Its achievements also included the first rolling lock gates, the largest movable dam built in the 19th century, and the widest chamber in world history.    

The largest rolled-earth fill dam in the world at the time of its completion, Denison Dam eventually served as a prototype for dam construction in future U.S. Army Corps of Engineers projects throughout the arid plains of the American Southwest. Procedures and equipment developed during its construction are now commonplace in the sampling and testing of soils.

Winding over 64 miles through the majestic San Juan mountains, the narrow-gauge railway known today as the Cumbres and Toltec Scenic Railroad was built as a branch of the extensive Denver and Rio Grande Western Railroad that ran through western Colorado and most of Utah. It originally served the large number of settlers flocking to the gold and silver mines of the region.

One of four single-track tunnels built by the Blue Ridge Railroad, the 4,273-foot Crozet Tunnel was constructed at a time when hand drills, pickaxes, and black powder amounted to state-of-the-art tunneling technology. At the time of its completion, it was the longest railroad tunnel in the world. Envisioned and built by Claudius Crozet, a French-born educator and civil engineer, the tunnel remains a testament to his belief in advancing rail transportation even when faced with numerous difficulties.