The site was just right for an arch dam, a narrow, sheer-walled canyon of dense granite. Buffalo Bill Dam--known as Shoshone Dam until 1946--is a gravity-arch cyclopean structure with a constant radius of 150 ft. Nearly 325 ft high and 108 ft thick at the base, it narrows to 10 ft along its 200-ft crest. To allay downstream fears, the first 82 ft from the foundation were designed as a gravity dam, but the remainder depends on arch action for strength.

"The design of the Shoshone dam is heralded...as a stride toward the day when dams shall be structures designed for the loads they are to carry," according to ENR predecessor Engineering News (6/9/10 p. 678). But the magazine also recognized public fears about the amount of mass in dams and noted that Buffalo Bill itself could have been built as strong and safe with just a quarter of the material.

Construction began in 1904 and was difficult from the start. The project's main source of water is melting snow from high country to the west. Because of floods, the working season was September to May. In the first year, a diversion flume was washed out, causing a year's delay. Flooding during the next summer caused a break in the log boom of an upstream sawmill, unleashing a log mass that destroyed the dam apron.

During the 1907-1908 winter, 86 ft of river channel was excavated to reach bedrock. Although the site was rich in solid granite, there was no local sand or gravel. These were produced from excavated granite. Cement was delivered by mule-drawn wagon from a railhead 7 miles away.

Buffalo Bill Dam was built of concrete studded with plums--rocks weighing from 25 to 200 lb. These were dropped by hand into each lift of freshly placed concrete. The projecting rocks helped to bond the next layer. Concreting had to take place during the worst times of the year, often at below freezing temperatures. Mix water was heated to near boiling by steam from boilers, which served to take frost from sand and gravel.

Buffalo Dam was completed in 1910 for $1 million. It survived two earthquakes in the area without damage.

1913
The Country's First Real Skyscraper

What were called skyscrapers in the 1890s and the early 20th Century were just buildings higher than most others, often just lumpish bulks. The first real skyscraper was the Woolworth Building in downtown New York City. At 760.5 ft, it was the world's tallest building. A slender tower soaring over everything, it truly scraped the sky.

The Woolworth Building was the creation of Frank W. Woolworth, who opened a five-and-ten-cent store in Lancaster, Pa., in 1879. By 1910, he owned 1,000 stores and set out to build an office building that would command the world's attention. Woolworth wanted a structure that was both modern and gothic. Architect Cass Gilbert and the engineering firm of Gunvald Aus and Co. designed his dream and The Thompson-Starrett Co. built it. It would be the tallest and most state-of-the-art structure, but with all the adornment of a medieval civic building clad in cream-colored, glazed terra cotta.

The project was a challenge from the ground up. The site, across from City Hall, was composed of alluvial mud and sand to a depth of more than 100 ft. The building stands on 66 reinforced concrete piers that were founded on bedrock by pneumatic caisson construction. Once the foundation was in place, work began simultaneously on steel erection and the building's below-grade floors 55-ft-deep.

The main portion of the Woolworth Building is 29 stories high and extends in two wings back 200 ft from the front elevation. The 85-ft-square tower rises from the 29th floor. At the 42nd floor, the tower is inset on all four sides. At the 48th, it is inset again. The copper roof rises from the 52nd to the 55th floor.

Coping with 30-psf wind loads was a major concern. The portal system of bracing makes up the principal element of lateral strength in the lower stories. The tower portion of the building is strengthened by girder and knee brace stiffening (Engineering News 7/20/14 p. 232). At the tower's two set-backs, wall columns do not have direct column support from below, but must be carried by girders. Where columns are offset, transfer of wind shear in the outer faces of the tower must be made by way of the floor. The Woolworth Building held onto its distinction as tallest skyscraper until 1930, when another landmark building--the Chrysler Building--was completed.