Byoir was born to Jewish immigrant parents from Poland but raised in Des Moines, Iowa.

Byoir's office was at 10 East 40th Street in New York, and from there he pursued his work in public relations, working with many other companies including the German Tourist Information Office, Freeport Sulphur Company, Crosley Motors, and Eastern Railroads.

In 1937, A&P, which had never engaged in political matters before, hired Byoir to help it fight the powerful anti-chain-store movement, which sought to break up big chains in order to protect independent retailers and wholesalers.

Working behind the scenes, Byoir organized a campaign to highlight the benefits of chains in reducing consumer prices.

The advertisement criticized a bill introduced by U.S. Rep. Wright Patman of Texas to impose punitive taxes on chain stores.