Crossword puzzle clue "abbr on a historic building"

Abbr. on a historic building

Historic site with a sign that says, "The immigrants have left the building"?

Org. with a National Historic Landmark building in lower Manhattan

One is perched atop Boston's historic Berkeley Building

Basic building block of basic building blocks

Building block of a building block

___ Building, company headquarters erected in 1908 in New York City, at the time the tallest building in the world

D.C.'s historic Metropolitan ___ Church: Abbr.