Intelligent Design (ID) has been called 'Creationism in a tuxedo'. The idea that some (or all) aspects of biology are not the result of blind evolution but rather have been designed that way by an intelligent something - though this something is often intentionally left vague - was posited by pseudoscientists who wanted to smuggle creationism into mainstream science and understood that if they mentioned the God word then they would likely be laughed out of court. They figured that by keeping religious ideas out of it, they could get it into schools and made several attempts to do so in the late 90's/early 2000's.
A Christian think-tank, The Discovery Institute, formulated what they called the 'Wedge Document' to change American culture by shaping public policy to reflect politically conservative fundamentalist evangelical Protestant values. One of the proponents of ID was Michael Behe, a professor of biochemistry at Lehigh University in Pennsylvania and senior fellow of the Discovery Institute. His book Darwin's Black Box he claimed that there was evidence, at a biochemical level, that some biological systems were "irreducibly complex". He thought that these systems could not, even in principle, have evolved by natural selection. He believed that the only possible alternative explanation for such complex structures was that they were created by an "intelligent designer". Of course this designer was never articulated. The Discovery Institute used Behe's ideas to promote ID to several US school districts as an alternative to evolutionary theory and one in Dover Pennsylvania became a focal point for the ideas after the school board recommended it be taught as part of the biology curriculum.
Some local residents fought back and at a 2005 trial brought by the parents (Kitzmiller v. Dover Area School District), Behe was called to the stand as an expert witness. He was forced to accept that his broadened definition of science, which encompassed ID, would also embrace astrology. The judge later wrote in his summation that: "The citizens of the Dover area were poorly served by the members of the Board who voted for the ID Policy. It is ironic that several of these individuals, who so staunchly and proudly touted their religious convictions in public, would time and again lie to cover their tracks and disguise the real purpose behind the ID Policy...". ID was now classed the same as creationism and not allowed to be taught in secular US schools.