By decade built

18,132 listed places have a construction year on record. This index groups them by decade, from the 1600s to the 2000s, with a page for each decade and for each state with 20 or more listings from it.

Construction years come from Wikidata, matched on National Register reference number, and only plain four-digit years are counted. Most listings have no year on record yet. Data refreshed September 19, 2026.