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The Chief Justice of the United States when William Rehnquist took office in 1986 was Ronald Reagan, the 40th president of the United States. Reagan, a Republican, served as president from 1981 until 1989. During his presidency, he appointed Rehnquist, an associate justice on the Supreme Court since 1972, to serve as the 16th Chief Justice of the United States. Rehnquist served in that role until his death in 2005.