The Teamsters Union was formed in 1903 by the joining of the Team Drivers International Union and the Teamsters National Union. Its full name is the International Brotherhood of Teamsters, Chauffers, Warehousemen, and Helpers of America. The majority of the members are truck drivers. It has been one of the few unions to have supported Republican candidates, Nixon in 1972, and Reagan in 1980.

At its formation, the strongest centers for Teamsters were Chicago, New York City, Boston and St. Louis. In fact, Chicago accounted for about half of the unions membership. It was in Chicago that the union attempted to strike against Montgomery Ward & Co. The strike was unsuccessful and union membership actually began to decline.

In 1907, one Daniel J. Tobin, a Boston Teamster that was unconnected to the strike became president. Remarkably, he held onto that position until 1952. His policy of avoiding sympathetic actions on behalf of other unions and guarding the expenditure of union funds helped the Teamsters to grow. In 1933, the union started organizing the rapidly growing long distance trucking industry. By threatening to stop deliveries to and from employers who refused to meet their terms, the Teamsters were able to gain contracts not only in trucking but in related businesses. Since 1940, the Teamsters have been the largest private sector union in the country. In 1998, they numbered about 1.4 million members.

In the 1940's the union began to run into touble in the form of corruption. An investigation by the Senate led the AFL-CIO to expel the Teamsters in 1957. Tobin's successor, one Dave Beck was sent to prison for larceny and income tax violations. Both Beck and his successor, Jimmy Hoffa, were called upon to testify in front of Senate investigative committee's. Their evasiveness before the committe's led to led to the passage of acts that limited the scope and power of the Teamsters Union.

Hoffa was sent to prison in 1967 but amazingly held onto the presidency until 1971. He resigned and was succeeded by Frank Fitzsimmons. Rumor has it that massive contributions from the Teamsters to Richard Nixon's reelection committe led to Hoffa's release in 1971. He attempted to regain the presidency in 1975 but disappeared under some extremely questionable circumstances.

The 1970's and 80's saw more trouble for the Teamsters. A number of the leadership were convicted of "irregularities" in handling the pension funds and of accepting bribes from employers to stop strikes or reduce labor costs. It got so bad that in 1977, the Union was forced to yield it's oversight of the pension fund to outside interests. In 1981, the new president, Roy Williams, was convicted of bribing a U. S. Senator. His successor, one Jackie Presser was indicted in 1985 for embezzling union funds and giving known crime figures no-show jobs.

As the 90's progressed the union faced tougher times. Deregulation in the trucking industry after 1980 has led to the creation of many low cost nonunion firms and to generally lower wages and benefits for union members.