The company I work for is headquartered in California so the rule from the top is no firearms on the premises, in the office or in the parking lot. Before COVID, I spent most of my time at client sites. None of them allowed either, but most were in Maryland. Good news is that several require badging in through security manned by armed guards.
That said, I’ve also been locked down at work severall times due to 2 armed robberies in the parking lot, an active shooter at a nearby mall, and a bear running around between buildings. The stupidest thing during those incidents were my coworkers rushing to the windows to see what’s going on.