Wikipedia has several lists of oldest buildings:
List of the oldest buildings in the world Oldest buildings in Canada by province or territory List of oldest buildings and structures in Toronto List of oldest buildings and structures in Macau Oldest buildings in the United Kingdom Oldest buildings in Scotland Oldest buildings in the United States List of the oldest buildings in Connecticut List of the oldest buildings in Delaware List of the oldest buildings in Massachusetts List of the oldest buildings in New Jersey List of the oldest buildings in New York List of the oldest buildings in Pennsylvania List of the oldest buildings in Rhode Island List of the oldest buildings in Virginia
See also List of the oldest churches in the United States List of the oldest churches in the world List of the oldest mosques in the world Oldest synagogues in the world