anals were built throughout the first half of the nineteenth century; most of them financed by state and local governments. The canal and river systems, though, eventually gave way to the "Iron Horse"-the locomotive. Railway lines proliferated and became the preferred mode of delivery. Railroads also proved essential to the development of the nation's ever-expanding western borders, and railroad hubs in cities such as Chicago were quickly established to transport crops of the plains back to eastern markets. By 1860 more than thirty thousand miles of railroad track had been laid--nearly as much as in the rest of the world combined. In the South, meanwhile, the region's economy was fused to the institution of slavery. Agricultural in nature, Southern business interests relied on slaves to harvest the cash crops (especially cotton) that were sold to customers in urban and industrial markets. As abolitionist pressures from the North grew, slave-holders grew increasingly concerned. Two issues dominated American politics in the first part of the nineteenth century: expansion and slavery. Perhaps inevitably, the two issues became tangled together over time, a development that contributed to the slide toward war that nearly tore the nation apart. After America's ill-fated attempt to annex Canada, the country turned its expansionist attention to the west. In the 1840s America wrested the republic of Texas and another large region (which included modern-day California, Nevada, Utah, and most of New Mexico and Arizona) away from Mexico. The mountains, deserts, and forests that comprised these territories were hundreds of miles away from the eastern United States, but their acquisition nonetheless had a tremendous impact on the relationship between the established Northern and Southern states. As the United States continued its expansion, it became increasingly difficult for it to maintain its balancing act between the North and the South regarding...
