While you may not find as many activists as opposed to DC, DC is probably the pinnacle. Like most of central Maryland, the area leans very left. I ran every street in Columbia two years ago, mostly around election time, and I saw countless signs for Democrats and literally only two houses with Trump signs. And one of those was a flag hanging inside a guy's garage, only open because he was washing his car. It's not common to find a place in the US where people are embarrassed to show support for Trump.

I've never lived in Boston, and only visited a few times, but I'd say it's similar enough. I'd say Boston is probably closer to Annapolis politically, where you have a good majority of Democrats, but there's enough old money people who are going to be conservative. Columbia has no old money :)