Yep, they grew up around Baltimore, so I'm sure they've been there quite a few times themselves.
Edit: Just found this.
Quote from the band:
"Merriweather Post Pavilion is an outdoor music venue in a place called Symphony Woods in Columbia, Maryland. It was designed by Frank Gehry in the 1960's, and they've been having concerts there from 1967 up through today. We used to go to shows there while growing up and have fond memories of times spent on the lawn. For most of the time we've been playing together, both in Animal collective and the years before, we've tried to make music that would be deserving of an amazing outdoor listening experience. As both a name and a place, Merriweather Post Pavilion represents this for us."
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