We made every effort to attribute a year or, at least, a range of years, for each postcard in this exhibit. In some cases, we were able to identify a specific year of publication. These, however, were not often found. Where a postcard contained a postmark, we cited the year of the postmark. If the postcard contained a historical subject that we could date (for example, postcards featuring the current Los Angeles City Hall would be no older than 1926), we used that to narrow a range of years. In some cases, we even took into consideration clothing or automobile styles or anything else that we could find in the postcard as clues to its date range. Where we found no clue to a postcard’s year or period, we fell back to the postcard's postcard era.