By what year was most (>75%) of the Urban population in the US served by sewage treatment plants?

The correct response highlights a significant milestone in urban sanitation and public health in the United States. By 1960, more than 75% of the urban population had access to sewage treatment plants, which marked a major advancement in sanitation efforts. This period followed the establishment of the Clean Water Act in 1948 and other public health initiatives that prioritized wastewater management to control pollution and protect water quality.

The increased availability of sewage treatment facilities by this time had profound effects on public health, as it reduced the incidence of waterborne diseases that were prevalent before such treatment systems were widely implemented. Access to these plants also started ensuring that treated waste did not contaminate local water supplies, further enhancing overall community health and sanitation.

This development laid the groundwork for continued investments in water infrastructure and environmental regulations, contributing to the broader efforts to protect public health and the environment throughout subsequent decades.