The research contains an analysis of the U.S. state environmental policy development in the second half of the 19th century and in the 20th century (up to early 1980s), which proceeded under the influence and with direct involvement of the American Conservationist Movement (later transformed into the American Green Movement). The author scrutinizes stages and milestones of the U.S. environmental legislation elaboration, state environmental policies under different presidential administrations up to the "turning point" (Ronald Reagan's election in 1981). Despite the traditional acute struggle for power between the two main U.S. political players - the Democratic Party and the Republican Party, presidential administrations of either had considered the nature protection activities an important integral part of domestic policy by default. By the beginning of 1980s, the American federal environmental legislation regulated the following issues: wilderness preservation; control over public fresh water systems, toxic agents, pesticide use; ocean dumping of shore-generated waste; rivers protection; cleaning of territory from radioactive wastes;pollutions scientific research; standard setting; ecological monitoring; law enforcement. Attention was also paid to acid rains, air visibility and global warming issues. The greatest part of currently functioning state environmental protection agencies had been created before the early 1980s boundary. The situation underwent a 180-degree turn in 1981 when President-Republican Ronald Reagan entered the office. Hence, the Republican Party representatives in power demonstrated a solely pragmatic approach to the environmental protection prioritizing the economic benefit. A correlation between the United States' historical development, specifics of the U.S. domestic environmental policy and its impact on the international environmental protection activities are also traced in the article.