The fort was constructed of coquina rock. Unique to Florida, the rock consists of millions of seashells cemented together. It proved highly durable and easily absorbed the force of many cannon balls.
The Castillo de San Marcos was the first permanent European settlement in the continental United States. Originally an outpost of the Spanish Empire, it is the oldest major engineered structure existing in America.
The Atlantic Ocean's northward-flowing Gulf Stream meets the southward-flowing Labrador Current at a point marked approximately by North Carolina's Outer Banks. Since the earliest days of United States commerce, shifting tides, inclement weather, treacherous shoals, and a low-lying shoreline there contributed to what soon became known as the Graveyard of the Atlantic. Warning sailors of this danger quickly became a top priority in the integrated system of navigational aids provided by the federal government to promote safe passage along the Atlantic Coast.
The idea of a canal eliminating the costly and dangerous sea trip around the Massachusetts peninsula of Cape Cod was envisioned as early as 1623 by Pilgrim leader Miles Standish. It was not until financier August Belmont became involved in 1906, however, that sufficient funds for the project could be raised. Belmont had been the primary backer of New York City's first subway, and chose the subway's chief engineer, William Barclay Parsons, as the canal's project director.
The Old Cape Henry Light house was the first construction project authorized by the First Congress. Constructed by John McComb, Jr. of New York City, this project set the stage for all subsequent public works projects of the Federal Government. In addition, this specific lighthouse was a vital navigation aid to all shipping through the Virginia Capes, thereby enhancing international and coastal trade with the Mid-Atlantic States.
For more than 174 years, the Canton Viaduct has stood as a dominating structure on the New England landscape. When completed in 1835, the slightly curved, granite masonry bridge - 615 feet long, 70 feet high, and 22 feet wide - carried a single track of the Boston and Providence Railroad, providing a critical link in the establishment of rail service between Boston and New York. In 1860, a second track was added. With few major alterations, the viaduct has continued to provide safe rail transportation to heavier and faster loads throughout the 20th century.
Cabin John Aqueduct, designed by Montgomery C. Meigs, conveys drinking water from Great Falls, Maryland to Washington, D.C. It was the longest stone masonry arch in the world for nearly 40 years. The segmental arch of the bridge has a span of 220 feet and a rise of only 57 feet. The main arch ring is built of cut and dressed granite. The secondary arch ring is radially-laid sandstone, of which the rest of the bridge is also constructed.
The Buffalo Bill Dam, known as the Shoshone Dam until 1946, was the first mass concrete dam in America. At nearly 325 feet high, it was also the tallest dam in the world at the time of completion.
During the post-Civil War era, efforts to cultivate the land for higher crop yields resulted in the digging of thousands of miles of ditches to improve land drainage. Accurately graded ditches were needed for open drainage, pipeline trenches and placement of underground agricultural drainage tile. Teams of skilled workers laid out the direction and gradient of a ditch and dug it out with pick and shovel. The Black Swamp area, where Lake Erie drains into northwest Ohio and southeast Michigan, was the center of much of the U.S. ditching activity.
