Question: Millennium Force is a steel roller coaster that was the 14th roller coaster to be built at Cedar Point amusement park, since what wooden roller coaster opened to the public on May 23, 1964?
Sentence (from "Griffon (roller coaster)"): Griffon was announced to the public on August 23, 2006 and opened on May 18, 2007 to positive reviews by both newspapers and enthusiasts.
Relevant evidence: No