The Blair Witch Project was released in 1999 and became a major phenomenon, also thanks in part to clever marketing, which utilized the Internet as a form of viral marketing in a major way for the first time. The website used fake news clippings & police reports which caused people to debate whether the movie was a real documentary or fake. The rookie actors were also listed as "missing" on IMDB to keep up appearances, and the movie was filmed using the "shaky cam" technique. It gave birth to the found footage horror genre, which has died down in recent years after endless mediocre Paranormal Activity sequels.
Blair Witch is actually the third film in the franchise, as a disappointing sequel titled Blair Witch 2: Book of Shadows was released to poor reaction in 2000. The third film has gotten a positive reaction at Comic-Con, and the trailer, which you can watch below, already makes it look much improved over Book of Shadows.