The booming wartime economy in Washington did not last. Recession followed the end of the war.
The government budgeted 22.9 million for war expenditures in 1861, but that had climbed to 1.03 billion by 1865.
The War Department put the expenditure for the Civil War at 2.73 billion.
Source: “Of Duty Well and Faithfully Done: A History of the Regular Army in the Civil War” by Clayton R. Newell, Charles R. Shrader, Edward M. Coffman