The Mainzer company was founded by brothers Renate and Alfred Mainzer, who started the business in their New York City home in 1938. They began by pasting animal, scenic, and floral postcards imported from Switzerland onto folders to be sold as greeting cards. They did this work in the evenings after their day jobs. As the business grew, they expanded into greeting cards and other postcards and moved into a rented facility. As these rented rooms became too small, in 1955 they bought the company's current warehouse in Long Island City, NY. In 1977, an additional building was added to house the company's offices. This information is useful in dating the Mainzer cards. Those bearing the 118 East 26th Street, NY address on the backs of the cards indicate that the cards were printed in 1955 or before. The Long Island address indicates that the cards were printed after 1955 but before 1977. The split address, 27-08 40th Avenue, was used on the cards after 1977.