A baseball card is a type of trading card relating to baseball, usually printed on some type of paper stock or card stock. A card will usually feature one or more baseball players or other baseball-related sports figures. Cards are most often found in the U.S. but are also common in countries such as Canada, Cuba, and Japan, where top-level leagues are present with a substantial fan base to support them. Some companies that are notable for making these cards include Topps, Upper Deck, and Panini. Previous manufacturers include Fleer (now a brand name owned by Upper Deck), Bowman (now a brand name owned by Topps), and Donruss (now a brand name owned by Panini Group). Baseball cards can be highly collectible and valuable.
While baseball cards were first produced in the United States, as the popularity of baseball spread to other countries, so too did the production of baseball cards. Sets appeared in Japan as early as 1898, in Cuba as early as 1909 and in Canada as early as 1912.
The obverse (front) of the card typically displays an image of the player with identifying information, including, but not limited to, the player's name and team affiliation. The reverse of most modern cards displays statistics and/or biographical information. Many early trade cards displayed advertisements for a particular brand or company on the back. Tobacco companies were the most instrumental in the proliferation of baseball cards, which they used as value added bonuses and advertisements for their products. Although the function of trading cards had much in common with business cards, the format of baseball cards most resembled that of playing cards — at least initially. For an example, one need look no further than the design of 1951 Topps Baseball.
While there are no firm standards that limit the size or shape of a baseball card, most cards of today are rectangular, measuring 2½ inches by 3½ inches (6.4 cm by 8.9 cm).
Since early baseball cards were produced primarily as a marketing vehicle, collectors began to classify those cards by the 'type' of company producing the set. The system implemented by Jefferson Burdick in The American Card Catalog has become the de facto standard in identifying and organizing trade cards produced in the Americas pre-1951. The catalog itself extends into many other areas of collecting beyond the sport of baseball. Sets like 1909–1911 White Borders, 1910 Philadelphia Caramels, and 1909 Box Tops are most commonly referred to by their ACC catalog numbers (T206, E95, and W555, respectively).