Best city for a 3 day weekend?

I need to get out of town once a month or so for work, and I like to take a weekend trip around that. I'm a young woman traveling alone - I'd appreciate recommendations for good cities (in the US) to spend, say, 3 days. I've done NYC a bunch, also Chicago. I'd like to avoid cities that are super masculine or party-focused, and I'm looking for places that are relatively walkable or have public transit. <br><br>I'm a bit of a history nerd, I like to try good restaurants, and museums, but I'd prefer some outdoor stuff too so I'm not just wandering in cities. <br><br>Any ideas?