There would be, on Saturday, June 10, an old-fashioned, conventional doubleheader, two games for a single-admission price. A common practice in Major League Baseball for a good part of the 20th century, traditional doubleheaders fell out of favor by the late 1980s, when rising attendance and escalating salaries led baseball owners to abandon them as an unnecessary giveaway since it amounted to a game’s being played free of charge.
Source: wiktionary