A month after the Battle of Antietam in Maryland, the bloodiest engagement of the Civil War, Union tax notices appeared in newspapers around the North. By passing a comprehensive tax bill, one small part of which was a tax on personal income, Congress conceded that the war would cost far more than any member had expected. On October 25, 1862, some 2,500 miles west of the battlefields, the inhabitants of Washington Territory first learned of the new income tax in the Washington Statesman of Walla Walla and in Olympia's Washington Standard. Newspapers of the period do not record how the territorial residents, who numbered fewer than the soldiers killed on either side at Antietam, initially reacted to modern taxation. From a territory immune from army conscription, not to mention the ravages of war, the Union asked a modest financial sacrifice. The law required payment only from individuals making in excess of $600 per year.
The Pacific Northwest Quarterly
Roberts, Phil (1988). "Taxing the Few: The First Federal Income Tax in Washington Territory." The Pacific Northwest Quarterly 79.2, 56-64.