Collecting baseball cards is still a popular hobby for children. But postcards are an excellent source of historical images, even of our sporting past.

Often the only pictures that can be found are of old buildings, street scenes or sports venues that are on cards buried in an old trunk in the attic.

Postcard collectors usually specialize. Some are interested in amusement parks, world fairs, sports, ships and trains. Trains have a great interest. If a train appears on a card, the price may double. Pictures of old sports stadiums also tend to command top dollar.

Vintage postcards of athletic events and venues, although not nearly as common as trains, exist, providing historians and anthropologists a "snapshot" of the past.

An interesting early sports postcard set was published by the Boston Post Card Company for the 1905 Ivy League football season. These cards depicted portraits of the players of each team arranged like the spots on a domino, hence called by publisher "Dominoe Cards."

One game represented was a controversial Harvard-Yale contest that almost led to the demise of college football due to an incident on the field between opposing players. College football was saved after President Theodore Roosevelt called a conference that rewrote the game's rules.

Views of sports arenas from the pioneer era (1893-1898) or golden age (1898-1915) of postcard production are rare, but fairly common from the linen era card (1930-1940s).

Since professional football is a more recent sport than pro baseball, football stadiums appear mostly on a newer color photo cards. However, many linen era cards can be found of college stadiums. The Rose Bowl, Princeton's Palmer Stadium, Cornell's Schoellkopf Stadium, the Yale Bowl and Harvard Stadium are a few listed.

Some of us can remember when life was simple and there were only 16 major league teams. Only three of the nostalgic stadiums of that era remain: Boston's Fenway Park (1912) with its notorious "Green Monster" left-field wall; Chicago's Wrigley Field (1914) with its ivy-covered red brick walls and New York's Yankee Stadium (1923), the "House that Ruth Built," home of the Bronx Bombers.

The other stadiums are gone, and postcard views command high prices. Who can forget Ebbets Field (1913-1957) where Jackie Robinson broke the color barrier and home of "dem bums,"the Brooklyn Dodgers (so named because Brooklynites were nicknamed "trolley dodgers" after the borrough's slow horse cars were replaced by faster electric trolley cars). Indeed the tears and jeers that went up when the Dodgers moved west in 1958 can still be heard.

A century ago, long before the advent of the pocket-sized point-and-shoot cameras, digital imaging and pictures by e-mail, the picture postcard was king. As a measure of their popularity, in a single day in 1906, some 200,000 postcards were mailed from Brooklyn's Coney Island. In the heyday of the postcard craze, over a billion cards were sold annually.

The hobby of collecting postcards even had its own name, "deltiology" and collectors were delitologists.The words are derive from the Greeks, meaning a collector of small writings or pictures.