This is a beetle in the family called Click Beetles (their scientific classification is Elateridae). Maryland is home to many species of click beetle, and in particular, this one appears to be species Aeolus mellillus (it has no common name), which is found throughout central Maryland. The larvae of this species chew into the stalks of live cereal plants (corn and other grains), so are not really much of a home landscape pest, but the adults (like many night-flying insects) are attracted to lights. If the bathroom has a window, perhaps they are being drawn to any light coming through it at night, or to the general side of the house if an outdoor light is used outside that wall. If so, sealing any gaps/cracks in that room can help exclude the beetles for the future, as would making sure the window weather-stripping and/or insect screening, if there is any, is intact. Using a curtain over the window can also cut down on any light coming through the glass that may be attracting nocturnal insects.

If there is a farm field in the general area which grows corn or wheat, or uses a rye cover crop in the off-season, maybe that's the primary source of the beetles. If the beetles are getting into the home from another room (say, by a front door whose weather-stripping is worn-down, near a porch light), they are also drawn to moisture, so a bathroom's higher humidity might be appealing to them, even if they aren't really feeding on anything in the home itself.

For now, all you need to do is just look for access points to seal and either capture the beetles and toss them outside or vacuum them up. Fortunately, they are not expected to cause any damage to the home itself; they're just a nuisance when abundant. Adult activity is peaking this time of year, but will not last all season.

Miri