Jobs and opportunities were in cities, in the mills and factories, which lead to once-farmers migrating to the cities to find work, and the shift from an agrarian to an industrial society. This tended to be a more South-to-North migration, as factories were located mostly in northern areas. The construction of the railroads, which began around 1830 and continued to expand, led to a much easier method of transportation than horse or foot; thus people were able to move much faster, which helped contribute to the rise in urban populations. As a response to the challenges of urban society, people began building "up" rather than "out", for homes, etc. due to the lack of space. Also, people began to have less children as they were not "needed", as they are within an agrarian society.
