How much did a 1975 stamp cost in 1975?

{| |- | First Class postage in 1975 was 10 cents for the first ounce. This rate was valid through December 31st of that year. At that point it went up to 13 cents. |}

Postage stamps of many different denominations were available in 1975. Assuming you meant to ask "How much did it cost to mail a letter in 1975?" the answer is: In the U.S. it cost 10 cents.

First class postage was 10 cents in the US in 1975.

{| |- | First Class postage in 1975 was 10 cents for the first ounce. This rate was valid through December 31st of that year. At that point it went up to 13 cents. |}

The cost of a first class stamp in 1975 was 10 cents. For a postcard it was 7 cents. Postcards went to 9 cents and First class went to 13 cents on December 31 1975.