In the United States, railroads spearheaded the second phase of the transportation revolution by overtaking the previous importance of canals. The mid-1800s saw a great expansion of American railroads. The major cities east of the Mississippi River were linked by a spiderweb of railroad tracks. Chicago's growth illustrates the impact of these rail links. In 1849 Chicago was a village of a few hundred people with virtually no rail service. By 1860 it had become a city of 100,000, served by eleven railroads.Farmers to the north and west of Chicago no longer had to ship their grain, livestock, and dairy products down the Mississippi River to New Orleans; they could now ship their products directly east. Chicago supplanted New Orleans as the interior of America's main commercial hub.

The east-west rail lines stimulated the settlement and agricultural development of the Midwest. By 1860 Illinois, Indiana, and Wisconsin had replaced Ohio, Pennsylvania, and New York as the leading wheat-growing states. Enabling farmers to speed their products to the East, railroads increased the value of farmland and promoted additional settlement. In turn, population growth in agricultural areas triggered industrial development in cities such as Chicago, Davenport (Iowa), and Minneapolis, for the new settlers needed lumber for fences and houses and mills to grind wheat into flour.

Railroads also propelled the growth of small towns along their routes. The Illinois Central Railroad, which had more track than any other railroad in 1855, made money not only from its traffic but also from real estate speculation. Purchasing land for stations along its path, the Illinois Central then laid out towns around the stations. The selection of Manteno, Illinois, as a stop of the Illinois Central, for example, transformed the site from a crossroads without a single house in 1854 into a bustling town of nearly a thousand in 1860, replete with hotels, lumberyards, grain elevators, and gristmills. By the Civil War (1861-1865), few thought of the railroad-linked Midwest as a frontier region or viewed its inhabitants as pioneers.

As the nation's first big business, the railroads transformed the conduct of business. During the early 1830s, railroads, like canals, depended on financial aid from state governments. With the onset of economic depression in the late 1830s, however, state governments scrapped overly ambitious railroad projects. Convinced that railroads burdened them with high taxes and blasted hopes, voters turned against state aid, and in the early 1840s, several states amended their constitutions to bar state funding for railroads and canals. The federal government took up some of the slack, but federal aid did not provide a major stimulus to railroads before 1860. Rather, part of the burden of finance passed to city and county governments in agricultural areas that wanted to attract railroads. Such municipal governments, for example, often gave railroads rights-of-way, grants of land for stations, and public funds.

The dramatic expansion of the railroad network in the 1850s, however, strained the financing capacity of local governments and required a turn toward private investment, which had never been absent from the picture. Well aware of the economic benefits of railroads, individuals living near them had long purchased railroad stock issued by governments and had directly bought stock in railroads, often paying by contributing their labor to building the railroads. But the large railroads of the 1850s needed more capital than such small investors could generate. Gradually, the center of railroad financing shifted to New York City, and in fact, it was the railroad boom of the 1850s that helped make Wall Street in New York City the nation's greatest capital market. The stocks of all the leading railroads were traded on the floor of the New York Stock Exchange during the 1850s. In addition, the growth of railroads turned New York City into the center of modern investment firms. The investment firms evaluated the stock of railroads in the smaller American cities and then found purchasers for these stocks in New York City, Philadelphia, Paris, London, Amsterdam, and Hamburg. Controlling the flow of funds to railroads, the investment bankers began to exert influence over the railroads' internal affairs by supervising administrative reorganizations in times of trouble.

在美国，铁路超越了运河在此之前的重要性，引领着交通运输革命第二阶段的发展。19世纪中叶见证了美国铁路大面积的扩张。密西西比河以东的主要城市由蜘蛛网一样纷繁交错的铁轨连接起来。芝加哥的发展就能够说明这些铁路带来的影响。在1849年，芝加哥是一个只有几百人的小村庄，几乎没有铁路服务。到了1860年，芝加哥已经发展为一个有着10万人口的大城市，有11条铁路贯穿其中。芝加哥北部和西部的农民不再需要用船装载他们的谷物、牲畜和乳制品，沿着密西西比河一路向下，运送到新奥尔良；他们现在可以直接将他们的产品运送到东部。芝加哥取代了新奥尔良成为了美国主要商业中心的腹地。 东西向的铁路促进了美国中西部地区聚落和农业的发展。到1860年，伊利诺斯州、印第安纳州和威斯康星州已经取代了俄亥俄州、宾夕法尼亚州和纽约市，成为了小麦的主要产地。铁路使农民加快了将农产品运输到东部的速度，提升了耕地的价值，并催生出了许多新的定居点。转而，农业地区的人口增长促进了芝加哥、达文波特（美国艾奥瓦州）、明尼阿波利斯等城市的工业发展，这是因为新移民需要木材来建造栅栏和房屋，需要用磨坊来把小麦磨成面粉。 铁路也推动了沿线小城镇的发展。1855年，伊利诺斯州中央铁路公司比其他铁路有更多轨道，它不仅能从交通运输中赚钱，还能从投资房地产中获利。伊利诺斯州中央铁路公司沿着铁轨购买土地建造新的车站，接着就在车站的周围建造了城镇。例如，伊利诺斯州中央铁路公司选择曼蒂诺（伊利诺斯州一处地名）建造了车站，使这个小村庄从1854年一个廖无人烟的岔道口转变为了1860年将近有一千人的繁华小镇，酒店、贮木场、谷物升降机、磨坊随处可见。直到内战开始（1861-1865），几乎没有人将铁路贯通的中西部地区看作是边疆地区，或是将那里的居民看成是拓荒者。 作为全国的第一大产业，铁路改变了企业的经营方式。在19世纪30年代早期，铁路，就像运河一样，依靠州政府的财政支持才能发展。然而，在19世纪30年代后期，经济大萧条的开始，使得州政府取消了规模过于宏大的铁路建设项目。选民们相信铁路让他们背负重税，让他们失去希望，转而反对政府为铁路建设提供财政援助，在19世纪40年代早期，一些州修改了自己的宪法，禁止为铁路和运河建设提供国家资金。联邦政府弥补了一些资金缺口，但是联邦政府的援助并没有成为1860年之前促进铁路发展的主要资金力量。相反，部分财政负担转移到了希望在当地建设铁路的农业地区的市、县政府身上。比如说，这样的市政府通常会给铁路公司路权、车站用地许可和公共资金。 然而，1850年铁路网络的急剧扩张，给当地政府的融资能力造成了不小的压力，铁路资金的需求转向了私人投资方向，而私人投资一直以来都是铁路资金来源的一部分。住在铁路附近的人很清楚铁路的经济效益，他们长期购买政府发行的铁路股票，并直接从铁路公司购买股票，他们通常通过参与铁路建设来支付股票费用。但是，19世纪50年代的大型铁路公司需要比这些小投资者所提供的资金更多的资本。渐渐地，铁路融资的中心转移到了美国纽约，事实上，是19世纪50年代铁路的蓬勃发展使纽约的华尔街成为了美国最大的资本市场。50年代所有主要铁路的股票都在美国纽约证券交易所中进行。此外，铁路的发展使纽约成为了现代投资公司的中心。这些投资公司评估了美国规模较小的一些城市的铁路股票，然后在纽约、费城、巴黎、伦敦、阿姆斯特丹和汉堡寻找这些股票的购买者。为了控制资金流向铁路，投资银行家们开始在困难时期通过监督行政重组的方式对铁路公司的内部事务施加影响。