Three Billboards Outside Ebbing, Missouri (2017)

The 2018 Oscar winner for Best Picture is a case of a film being inspired by true events, rather than being entirely based on them. The main premise of a grieving parent using billboards on a highway to criticize a local police department's failure to solve a crime is taken from actual events in Vidor, Texas. In the true-life case, police ignored the parents of the murdered victim in 1991 and facts that would have led them to an alleged hometown hero from an old-money family.  With the case remaining unsolved, the billboards that inspired the film are actually still up on Interstate 10.