On January 8, 1861, United States troops stationed at Ft. Barrancas, Pensacola Bay, Florida opened fire at the local state militia trying to take the fort.
The Federal troops withdrew 2 days later. U.S. troops successfully defended Fort Pickens, Pensacola, Florida, and Fort Taylor in Key West.
There were other episodes where gunfire erupted...Kansas, Missouri come to mind. Next was cannon fire......the Harriet Lane, a federal gunboat in Charleston Harbor, the night of April 11, and cannon fire in Charleston Harbor the next morning.
But war is started by the men that could order the weapons and soldiers into action. No one had the resources or motivation to instigate war at this time other than Lincoln. The war began when real acts of war occurred...the blockade and the state militia troop call ups by Lincoln.
So, the war began in Washington.
What about the cannon fire from the rebel batteries directed at the Rhoda A. Shannon the week before? Don't those count? Never mind the fire directed at the Star of the West in January. Wouldn't those have been among the first shots fired?