Harvey R. Ball, the strongest claimant to having invented the smiley face, that 100-watt yellow grin adorning tote bags, letters, car bumpers, cycling shorts and eventually a United States postage stamp, died on Thursday in Worcester, Mass. He was 79.

The cause was liver failure, said his daughter, Jacquelyn Stein.

As Mr. Ball told it, in 1963 he was running an advertising and public relations agency in Worcester when a client, the State Mutual Life Assurance Company of America -- now Allmerica Financial Corporation -- asked him to help soothe the ruffled feelings of workers when it merged with another company.

Mr. Ball came up with the smiley face.

Mr. Ball later told interviewers that he was paid $45 for his artwork and never applied for a trademark or copyright.

At its peak of popularity, in 1971, more than 50 million smiley face buttons were sold, The Associated Press reported. In 1999, the Postal Service issued a smiley face stamp.