Rapid urbanization in the late 19th/early 20th century led to overcrowding, unsanitary housing, unsafe drinking water, high crime rates, fires, and inadequate transportation systems in many American cities. Reformers attempted to address these urban problems through measures like developing public water and sewer systems, introducing water filtration and chlorination, establishing full-time police and fire departments, replacing wooden buildings with brick and stone, and creating settlement houses to provide social services to the poor.