Was Boston Ever the U.S. Capital?

No. Boston has never been the capital of the United States.

The U.S. capital moved several times before settling permanently in Washington, D.C.:

1. Philadelphia (1774–1783, intermittently) – First Continental Congress, Second Continental Congress, Congress of the Confederation.
2. Princeton, NJ (1783) – Nassau Hall.
3. Annapolis, MD (1783–1784) – Maryland State House.
4. Trenton, NJ (1784) – French Arms Tavern.
5. New York City (1785–1790) – Federal Hall (first U.S. Congress, Washington's inauguration).
6. Philadelphia (1790–1800) – Temporary capital per Residence Act.
7. Washington, D.C. (1800–present) – Permanent capital.

Boston was the capital of the Massachusetts Bay Colony (1630–1686, 1689–1692) and later the Commonwealth of Massachusetts (1780–present), but never the national capital.