People have been giving each other “the finger” since Ancient Greece. The first documented use is said to be a photograph from 1886 in which the pitcher for the Boston Beaneaters extends his middle finger to the camera (ostensibly to the rival New York Giants). Even though it’s been around for so long, many still find the gesture offensive enough to try to bring criminal charges. Courts have ruled that “flipping the bird” is a form of speech protected by the First Amendment. It’s not a crime to be obnoxious. But there’s a man in Oregon named Robert Ekas who tests the limits of free speech by giving the finger to every police officer that he sees.
To learn more about the legalities of the middle finger, you might enjoy “Digitus Impudicus: The Middle Finger and the Law” from the UC Davis Law Review.