Massachusetts Secretary of State William Galvin said the 1775 letter from Joseph Warren was discovered in a Sotheby's catalog of Revolutionary War manuscripts. The state negotiated the letter's return.
At the time, Warren was a doctor and president of the Provincial Congress that sat in Watertown, Mass. In the letter, he said he had just learned that Col. Benedict Arnold had captured Fort Ticonderoga, N.Y., and forts at Crown Point and St. John's in the Lake Champlain area, which reduced the threat of British attack from Canada.
Warren died the same year in the Battle of Bunker Hill.