MA

The Choate Bridge of Essex County, completed in 1764, is the oldest documented two-span masonry arch bridge in the United States. Named after Colonel John Choate, who supervised the construction, the bridge is located on South Main Street and spans the Ipswich River. Originally, the bridge measured 80 feet 6 inches long and 20 feet 6 inches wide. In 1838 it was widened to 35 feet 6 inches on the east side in order to accommodate another lane of traffic. The west side and the parapet of the bridge, along with the inscription to Colonel Choate, remained unchanged.

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.  

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.

By the 1890s, the transportation infrastructure of downtown Boston - a maze of narrow, winding streets laid out, in some cases, along Colonial cow paths - proved completely inadequate for the needs of a modern, bustling metropolis. Tremont Street, the city's main thoroughfare, was regularly subject to gridlock from a convergence of foot traffic, horse-drawn conveyances, trolley lines, and electric streetcars. To rectify the problem, the Boston Transit Commission, with Howard A. Carson as chief engineer, was created in 1894 to study remedies. 

The Saugus Ironworks, the first commercial ironworks in North America, was an impressive technological achievement for an early colony. The same basic processes are used today: reducing iron oxide with carbon to produce metallic iron that can be cast in a mold, producing wrought iron by puddling cast iron, and fabricating wrought iron with power hammer and rolls.

This hydraulic closed-die press, among the largest fabrication tools in the world, has had a profound influence in America's leading role in commercial aircraft, military aircraft, and space technology. As part of the same Heavy Press Program that created the Mesta press, the Wyman-Gordon press was designed by the Loewy Construction Company and began operating in October 1955. Among its contributions was the development of the new jetliner Boeing 747 in the 1960s.

Much of the sophisticated system of canals, dams, gates, and tunnels built to manage water power in 19th-century Lowell is preserved today as the basis of the Lowell National Historical Park and the Lowell Heritage State Park. Pictured above is the Boott Penstock, an early channel adjacent to the Boott Mills (right).