The Houston Astros won their second pennant in franchise history on Saturday, and it marked a historic moment not seen by baseball fans in well over a century.
When George Springer squeezed the final out to clinch the Astros' first-ever American League pennant it marked the first time in the modern era (since 1901) that the same team has reached the World Series while representing two different major leagues. In 2005, the Astros - then part of the National League - played in the Fall Classic as champions of the NL.
The last time the same franchise represented two different leagues in a World Series was some 127 years ago. The Brooklyn Bridegrooms - a franchise now known as the Los Angeles Dodgers - won the American Association pennant in 1889, then immediately switched leagues and took the NL crown in 1890.
In both those years the Bridegrooms participated in a "World Series" championship between the AA and NL winners. As the American Association representative they defeated the NL champion New York Giants 6-3 in the 1889 series; one year later, the NL pennant-winning Bridegrooms then tied the AA's Louisville club 3-3-1. That 1890 World Series was the final one contested until 1903.
Today, those 19th-century World Series are often considered to be "unofficial" despite following the same general format (the champions of baseball's two major leagues) as today's Fall Classic.
In addition to the Astros and Bridegrooms/Dodgers, a third major-league franchise - the Boston Reds - can also lay claim to winning pennants in two major leagues, having won both the lone Players' League pennant in 1890 and the final AA title in 1891 before disbanding. Unlike the Bridegrooms and Astros, however, the Reds did not participate in any postseason series after their pennants.
The Astros, established in 1962 as the Houston Colt .45s, played their first 50 seasons as members of the National League. They made the NL playoffs nine times in those 50 years before moving to the AL in 2013.
Only the Astros and Milwaukee Brewers (AL to NL in 1998) have switched leagues in modern era. Although the Brewers have made the NL playoffs since moving to the Senior Circuit, their lone pennant and World Series appearance came as an AL club in 1982.