Count your blessings: If it were 1913, your federal income taxes would be six weeks overdue. March 1 was the original deadline specified by the United States Congress after the 16th Amendment - which permits the levying of an income tax - was ratified. But the history of the tax dates to 1862, when the Lincoln administration instituted an income tax to pay for the Civil War. The tax was (finally) repealed 10 years later. And when it was revived by Congress in 1894, the US Supreme Court ruled it unconstitutional - hence the 16th Amendment. Congress extended the deadline to March 15 several years later, and in 1955 moved it to April 15 - probably so Uncle Sam could hold on to your refund a while longer.
Sources: Business Reference Services, United States Library of Congress; Internal Revenue Service; Fortune, April 15, 2002.