Cities reacted by paving streets, digging sewers, sanitising water, building housing, and establishing public transportation systems. Not only did urbanisation increase the population of cities, but it also increased the height and size of buildings. And therefore, it created many opportunities for Americans to get jobs, the economy was becoming balanced in some ways, along with technological innovations in transportation and housing construction, encouraged migration to cities. Development of railroads, streetcars, and trolleys in the 19th century enabled city boundaries to expand. People no longer had to live within walking distance of their jobs.
