1862 - President Lincoln signed into law a revenue-raising measure to help pay for Civil War expenses. The measure created a Commissioner of Internal Revenue and the nation's first income tax. It levied a 3 percent tax on incomes between $600 and $10,000 and a 5 percent tax on incomes of more than $10,000.
1867 - Heeding public opposition to the income tax, Congress cut the tax rate. From 1868 until 1913, 90 percent of all revenue came from taxes on liquor, beer, wine and tobacco.
1872 - Income tax repealed.
1894 - The Wilson Tariff Act revived the income tax and an income tax division within the Bureau of Internal Revenue was created.
1895 - Supreme Court ruled the new income tax unconstitutional on the grounds that it was a direct tax and not apportioned among the states on the basis of population. The income tax division was disbanded.
1909 - President Taft recommended Congress propose a constitutional amendment that would give the government the power to tax incomes without apportioning the burden among the states in line with population. Congress also levied a 1 percent tax on net corporate incomes of more than $5,000.
1913 - As the threat of war loomed, Wyoming became the 36th and last state needed to ratify the 16th Amendment. The amendment stated, "Congress shall have the power to lay and collect taxes on incomes, from whatever source derived, without apportionment among the several states, and without regard to any census or enumeration." Later, Congress adopted a 1 percent tax on net personal income of more than $3,000 with a surtax of 6 percent on incomes of more than $500,000. It also repealed the 1909 corporate income tax. The first Form 1040 was introduced.
1918 - The Revenue Act of 1918 raised even greater sums for the World War I effort. It codified all existing tax laws and imposed a progressive income-tax rate structure of up to 77 percent.
1919 - The states ratified the 18th Amendment, barring the manufacture, sale or transport of intoxicating beverages. Congress passed the Volstead Act, which gave the Commissioner of Internal Revenue the primary responsibility for enforcement of Prohibition. Eleven years later, the Department of Justice assumed primary prohibition enforcement duties.
1931 - The IRS Intelligence Unit used an undercover agent to gather evidence against gangster Al Capone. Capone was convicted of tax evasion and sentenced to 11 years.
1933 - Prohibition repealed. IRS again assumed responsibility for alcohol taxation the following year and for administering the National Firearms Act. Later, tobacco tax enforcement was added.
1942 - The Revenue Act of 1942, hailed by President Roosevelt as "the greatest tax bill in American history," passed Congress. It increased taxes and the number of Americans subject to the income tax. It also created deductions for medical and investment expenses.
1943 - Congress passed the Current Tax Payment Act, which required employers to withhold taxes from employees' wages and remit them quarterly.
1944 - Congress passed the Individual Income Tax Act, which created the standard deductions on Form 1040.
1952 - President Truman proposed his Reorganization Plan No. 1, which replaced the patronage system at the IRS with a career civil service system. It also decentralized service to taxpayers and sought to restore public confidence in the agency.
1953 - President Eisenhower endorsed Truman's reorganization plan and changed the name of the agency from the Bureau of Internal Revenue to the Internal Revenue Service.
1954 - The filing deadline for individual tax returns changed from March 15 to April 15.
1961 - The Computer Age began at IRS with the dedication of the National Computer Center at Martinsburg, W.Va.
1965 - IRS instituted its first toll-free telephone site.
1972 - The Alcohol, Tobacco and Firearms Division separated from the IRS to become the independent Bureau of Alcohol, Tobacco and Firearms.
1974 - Congress passed the Employee Retirement and Income Security Act, which gave regulatory responsibilities for employee benefit plans to the IRS.
1986 - Limited electronic filing began. President Reagan signed the Tax Reform Act, the most significant piece of tax legislation in 30 years. It contained 300 provisions and took three years to implement. The Act codified the federal tax laws for the third time since the Revenue Act of 1918.
1992 - Taxpayers who owed money were allowed to file returns electronically.
1998 - Congress passed the IRS Restructuring and Reform Act, which expanded taxpayer rights and called for reorganizing the agency into four operating divisions aligned according to taxpayer needs.
2000 - IRS enacted reforms, ending its geographic-based structure and instituting four major operating divisions: Wage and Investment, Small Business/Self-Employed, Large and Mid-Size Business and Tax Exempt and Government Entities. It was the most sweeping change at the IRS since the 1953 reorganization.
2001 - IRS administered a mid-year tax refund program to provide advance payments of a tax rate reduction.
2003 - IRS administered another mid-year refund program, this time providing an advance payment of an increase in the Child Tax Credit. Electronic filing reached a new high - 52.9 million tax returns, more than 40 percent of all individual returns.