Some background: under US law — and under a mountain of international treaties, from the Berne Convention to the TRIPS —copyright is automatically granted to creative works of human authorship “at the moment of fixation in some tangible medium.”
That is: as soon as a human being makes something creative, and records it in some medium (a hard-drive, magnetic tape, paper, film, canvas, etc), that creative thing is immediately copyrighted (the duration of that copyright varies, both by territory and by whether the creator was working on their own or for a corporation).