How were overcrowded cities solved in the 19th century?

For the first half of the 19th century the rural and urban poor had much in common: unsanitary and overcrowded housing, low wages, poor diet, insecure employment and the dreaded effects of sickness and old age

Explanation:

several states had passed similar laws, but they were limited to intrastate businesses. the sherman antitrust act was based on the constitutional power of congress to regulate interstate commerce.

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