In 1970, a first-class postage stamp in the United States cost 6 cents, and a postcard stamp cost 5 cents. The first-class postage rate was raised to 8 cents on May 16, 1971.
In 1970, each additional ounce mailed at a first-class rate cost 6 cents, and packages started at 6 cents per ounce as well. The 6-cent rate began on January 7, 1968. The 1971 rate increase was the first increase set by the Postal Regulatory Commission under the Postal Reorganization Act of 1970. The 1968 rate increase that brought first-class postage to 6 cents was the first rate increase after the implementation of the ZIP code system.