Firefighters battle the 1969 Cuyahoga River fire.

Firefighters battle a fire on Ohio's Cuyahoga River in 1952. The 1969 blaze, one of nine on the river since 1868, came at a time of increasing environmental awareness and symbolized years of environmental neglect. This, in turn, helped spur grassroots activism that resulted in a wave of federal legislation devoted to clean air, clean water, and natural resource protection.

Credit: United Press International