The Lanham Act (also known as the Trademark Act of 1946) is the federal statute that governs trademarks, service marks, and unfair competition. It was passed by Congress on July 5, 1946, and signed into law by President Harry Truman. The Act took effect on July 5, 1947.
A trademark is a word, phrase, logo, graphic symbol, or other device that identifies the source of a product or service and distinguishes it from competitors. Some examples of trademarks are Ford (cars and trucks), Betty Crocker (food products), and Microsoft (software). A service mark is the same as a trademark, except that it promotes a service, such as FedEx (delivery services).
The Lanham Act sets out procedures for federally registering trademarks, states when owners of trademarks may be entitled to federal judicial protection against infringement, and establishes other guidelines and remedies for trademark owners.
The Lanham Act, also known as the Trademark Act of 1946, is codified at 15 U.S.C. §1051 et seq.
You can find the Lanham Act, as amended today, at Cornell University Law Schools Legal Information Institute.