February 17 – Miami University (Ohio) is established (by Act of February 2) on the township of land required to be set aside for it under the conditions of the Miami Purchase in 1794.
February 20 – A decision by the Supreme Court of the United States states that the power of the federal government is greater than any individual state.
August – Following refitting, the USS Constitution ("Old Ironsides") is recommissioned as the flagship of the North Atlantic Squadron.[2]
October 11 – Along the Natchez Trace in Tennessee, explorer Meriwether Lewis dies under mysterious circumstances at an inn called Grinder's Stand. It is considered an alleged suicide though some evidence suggests murder.
William S. Appleton, Robert C. Winthrop. "Original Bank Circular, 1809". Proceedings of the Massachusetts Historical Society, Vol. 11, (1869–1870)
Thomas H. Shoemaker. A List of the Inhabitants of Germantown and Chestnut Hill in 1809. The Pennsylvania Magazine of History and Biography, Vol. 16, No. 1 (April, 1892), pp. 42–63
An Itinerary to Niagara Falls in 1809. The Pennsylvania Magazine of History and Biography, Vol. 24, No. 2 (1900), pp. 200–202
Ellmore Barce. Governor Harrison and the Treaty of Fort Wayne, 1809. Indiana Magazine of History, Vol. 11, No. 4 (1915), pp. 352–367
Charles Lyon Chandler. United States Shipping in the La Plata Region, 1809–1810. The Hispanic American Historical Review, Vol. 3, No. 2 (May 1920), pp. 159–176
Joshua Gilpin. Journal of a Tour from Philadelphia Thro the Western Counties of Pennsylvania in the Months of September and October, 1809. The Pennsylvania Magazine of History and Biography, Vol. 50, No. 1 (1926), pp. 64–78
A trip from Fort Wayne to Fort Dearborn in 1809. Indiana Magazine of History, Vol. 36, No. 1 (1940), pp. 45–51
Edwin J. Hipkiss. A Cabinetmaker's Bill: Boston, 1809. Bulletin of the Museum of Fine Arts, Vol. 45, No. 259 (February, 1947), pp. 12–14
Noble E. Cunningham Jr. The Diary of Frances Few, 1808–1809. The Journal of Southern History, Vol. 29, No. 3 (August, 1963), pp. 345–361
William G. McLoughlin. Thomas Jefferson and the Beginning of Cherokee Nationalism, 1806 to 1809. The William and Mary Quarterly, Third Series, Vol. 32, No. 4 (October, 1975), pp. 548–580.
Jeffrey A. Frankel. The 1807–1809 Embargo Against Great Britain. The Journal of Economic History, Vol. 42, No. 2 (June, 1982), pp. 291–308.
James M. O'Toole. From Advent to Easter: Catholic Preaching in New York City, 1808–1809. Church History, Vol. 63, No. 3 (September, 1994), pp. 365–377