By 1905, all U.S. towns with population over 4,000 have city sewers. Baltimore sewer system, begun 1915, last city to build comprehensive system. 1857 State of Vermont commissions study on depleted fish populations in Connecticut River. George Perkins Marsh gets the job. 1857 Frederick Law Olmstead begins commission to develop New York's Central Park.
Federal government grants state of California land for Yosemite Valley Park.
Some 18,000 people are living in cellars below the high water mark. At high tide the water often wells up through the floors, submerging them to a considerable depth. Founding of the American Society for the Prevention of Cruelty to Animals. Pennsylvania legislature rejects bill to regulate water pollution, despite heavy industrial pollution in Delaware River. 1869 Massachusetts State Board of Health formed.