At the end of the nineteenth century, there were basically two kinds of buildings in the United States. On one hand were the buildings produced for the wealthy or for civic purposes, which tended to echo the architecture of the past and to use traditional styles of ornamentation. On the other hand were purely utilitarian structures, such as factories and grain elevators, which employed modern materials such as steel girders and plate glass in an undisguised and unadorned manner. Such buildings, however, were viewed in a category separate from “fine” architecture, and in fact were often designed by engineers and builders rather than architects. The development of modern architecture might in large part be seen as an adaptation of this sort of functional building and its pervasive application for daily use. Indeed, in this influential book Toward a New Architecture, the Swiss architect Le Corbusier illustrated his text with photographs of American factories and grain storage silos, as well as ships, airplanes, and other industrial objects. Nonetheless, modern architects did not simply employ these new materials in a strictly practical fashion--they consciously exploited their aesthetic possibilities. For example, glass could be used to open up walls and eliminate their stone and brick masonry because large spaces could now be spanned with steel beams.

The fundamental premise of modern architecture was that the appearance of the building should exhibit the nature of its materials and forms of physical support. This often led to effects that looked odd from a traditional standpoint but that became hallmarks of modern architecture for precisely this reason. For example, in traditional architecture, stone or brick walls served a structural role, but in a steel-beam building the walls were essentially hung from the internal skeleton of steel beams, which meant that walls and corners no longer needed to be solid but could be opened up in unexpected ways. At the Fagus shoe factory in Germany, for example, German architect Walter Gropius placed glass walls in the corners, effectively breaking open the box of traditional architecture and creating a new sense of light and openness. Similarly, steel beams could be used to construct balconies that projected out from the building without any support beneath them. These dramatic balconies quickly became a signature of modern architects such as Frank Lloyd Wright. Wright’s most dramatic residence, Fallingwater, has balconies that thrust far out over a stream in a way that seems to defy gravity.

The ways in which new technology transformed architectural design are dramatically illustrated through the evolution of the high-rise office building. After ten or twelve stories, masonry construction reaches a maximum possible height, since it runs into difficulties of compression and of inadequate lateral strength to combat wind shear. Steel construction, on the other hand, can support a building of 50 or 100 stories without difficulty. Such buildings were so different from any previous form of architecture that they quickly acquired a new name--the skyscraper.

From the standpoint of real estate developers, the purpose of skyscrapers was to increase rental space in valuable urban locations. But to create usable high-rise buildings, a number of technical challenges needed to be solved. One problem was getting people to the upper floors, since after five or six stories it becomes exhausting to climb stairs. Updated and electrified versions of the freight elevator that had been introduced by Elisha Graves Otis in 1853 (several decades before skyscraper construction) solved this problem. Another issue was fire safety. The metal supporting buildings became soft when exposed to fire and collapsed relatively quickly. (They could melt at 2700 Fahrenheit, whereas major fires achieve temperatures of 3000degrees). However, when the metal is encased in fire-retardant materials, its vulnerability to fire is much decreased. In Chicago, a system was developed for surrounding the metal components with hollow tiles made from brick-like terra-cotta. Such tiles are impervious to fire. The terra-cotta tiles were used both to encase the supporting members and as flooring. A structure built with steel beams protected by terra-cotta tiles was still three times lighter than a comparably sized building that used masonry construction, so the weight of the tiles was not a problem.

19世纪末期，美国主要有两类建筑。一种是为富人或为公共目的建造的建筑物，倾向于仿制过去的建筑，并使用传统风格的装饰物。另一种纯粹是功能性建筑，比如工厂和有升降机设备的谷仓，使用现代材料如钢梁和厚玻璃板，风格朴素，基本没有装饰。但是这种建筑物，属于与观赏性建筑不同的类别，它们实际上通常是由工程师和施工人员设计的，而不由建筑师设计。现代建筑的发展可能在很大程度上可以看作是对此类功能性建筑以及对广泛日常用途的改编和适应。确实，在《走向新建筑》这本非常有影响力的书中，瑞士建筑师勒•柯布西耶阐述内容时使用了美国工厂、粮仓、船只、飞机还有其他工业物品的照片。尽管如此，现代建筑师并不是简单地利用这些物品来打造完全实用的样式，他们有意识地开发它们的美学可能性。例如，玻璃可以用来代替墙，消除石头和砖砌工程，因为广阔的空间现在可以由钢梁支撑。

现代建筑的基本前提是建筑的外形应当展示所使用材料的特性和物理支撑的形式。这通常会造成的效果是站在传统的立场上看很奇怪，但也恰恰成为了现代建筑的标志。例如，传统建筑中，石墙或砖墙是框架结构之一，而在钢梁建筑中，墙体基本上是悬挂在内部钢梁框架上，也就是说墙和角落不再需要固定，可以以出人意料的方式打开。比如，在德国Fagus鞋厂，德国建筑师沃尔特•格罗佩把玻璃墙放在各个角落，有效打破了传统建筑的限制，创造出新的光感和开放感。同样地，钢梁可以被用来建造那些从楼体延伸出来且下方没有支撑物的阳台。这些引人注目的阳台很快就成了像弗兰克•劳埃德•赖特这类现代建筑师的代表。赖特最有名的作品是跌水别墅，溪流以一种看起来好像是反重力的方式穿过阳台。

新技术改变建筑设计的方式显然可以通过高层办公大楼的演变来体现。10-12层楼是砖石结构建筑能达到的最大高度，因为面对风切变，它会陷入压缩和横向强度不足的困境。另一方面，钢结构可以毫不费力地支撑50-100层的大楼。这些大楼与之前建筑的形状如此不同，以至于它们迅速有了自己的名字——摩天大楼。

站在房地产开发商的角度来看，摩天大楼的目的是增加原本就高价的城市区域的可租赁面积。但是为了建造可用的高楼，需要解决许多技术难题。难题之一就是如何把人运送到上部楼层，因为在爬了5-6层楼后，人们会筋疲力尽。伊莱沙•格雷夫斯•奥的斯在1851年引进了现代电气化货物升降梯（在摩天大楼建设的数十年前），解决了这个难题。另一个问题是消防安全。这种由金属支撑的建筑物，遇火后会变软，然后以相对较快的速度坍塌。（它们的熔点是2700华氏度，而大火通常能达到3000度。）但是，当金属包裹在防火材料中时，火对它的伤害性会大大降低。在芝加哥，一个用于包裹金属构件的、由类似砖的赤陶土构成的空心砖系统被开发出来。这种空心砖防火，既可以用来包裹承重构件，也可以铺在地上。一个由钢梁构成并且受到赤陶土空心砖保护的建筑，比大小相当的由砖石构造的建筑物要轻上3倍，因此空心砖的重量并不是问题。