Supposedly, this photo dates from 1922 Chicago and presents the arrest of women at the beach whose demonstrative crime was to wear one-piece bathing suits that bared and exposed their legs. It’s Naked Protesters material because the scene is clearly a media circus; it seems at least possible that the ladies in question were flouting the contemporary sartorial regulations with intent to protest them and make a scene.
However, the explanation opens with “supposedly” because this picture is all over the internet under similar captions, none of which offer an authoritative source of the captioning information. The most commonly cited modern appearance of this photo is a Reddit thread from October 2011 with the caption “Women in Chicago being arrested for wearing one piece bathing suits, without the required leg coverings. 1922.” Most other web appearances cite the Reddit thread or lightly rephrase the Reddit caption, but the photo can also be found on a other websites with similar captions dated to the few months prior to the Reddit thread. Not found were any older appearances on the web, nor any authoritative sources for the photo that might be used to confirm the many similar captions.