The Palace of the Governors.
The pentagon
pentagon
It is in New Mexico. The building, called the Hall of Governors, is in the capital city of Santa Fe.
The pentagon.
It is believed to be a fort in Florida that was built by the Spainyards in the 1500s. Now it is just ruins but can be visited in Florida.
There are many thousands of government buildings in the US. The seat of the Federal government is in Washington DC.
Fort Sumter
I don't know ask some one else
The US does not and never has had a new government name
The capitol building is the meeting place of the US Congress which is the legislative branch of the US government.
Appalachian Mountains (oldest in US)