Earth Day, an event to increase public awareness of the world's environmental problems, is celebrated in the United States for the first time. It was the ＿＿（21）＿＿ of Senator Gaylord Nelson of Wisconsin, a staunch environmentalist who hoped to provide unity to the grassroots environmental movement and increase ecological awareness. "The ＿＿（22）＿＿ was to get a nationwide demonstration of concern for the environment so large that it would shake the political establishment out of its lethargy," Senator Nelson said, "and, finally, ＿＿（23）＿＿ this issue permanently onto the national political agenda." Earth Day indeed increased environmental awareness in America, and in July of that year the Environmental Protection Agency was established by special executive order to ＿＿（24）＿＿ and enforce national pollution legislation. On April 22, 1990, the 20th anniversary of Earth Day, more than 200 million people in 141 countries ＿＿（25）＿＿ in Earth Day celebrations. Earth Day has been celebrated on different days by different groups internationally. The United Nations officially celebrates it on the vernal equinox, which usually occurs about March 21.