The Lone Star Series (also known as the Silver Boot Series) is a Major League Baseball (MLB) rivalry featuring Texas' two major league franchises, the Houston Astros and Texas Rangers. It is an outgrowth of the "natural rivalry" established by MLB as part of interleague play as the Rangers are a member of the American League (AL) and the Astros were a member of the National League (NL) until . During interleague play, the winner of the six game series was awarded the Silver Boot, a tall display of a size 15 cowboy boot cast in silver, complete with a custom, handmade spur. If each team had won three games each for a tie, the declared winner was the team that scored the most runs over the course of the series. In , the Astros joined the American League West with the Rangers and changed their rivalry from an interleague to an intradivision one with nineteen games played. Background The Greater Houston and Dallas–Fort Worth metroplex (DFW) areas have been rivals in sports and other areas for many years. Differences, not related to baseball, include the weather during the summer, population, cultural, and allegiance preferences between the different regions of Texas. Both Greater Houston and DFW have humid subtropical climates; however, DFW mostly has dry winds in the summer and sometimes icy conditions in the winter, with some frost at night, compared to Greater Houston's severe relative humidity and minimal wind, except near the coast, and milder winter conditions. The Metroplex is located inland in North Texas while Houston is in the face of the Gulf of Mexico in Southeast Texas. The city of Dallas has the 9th largest population in the United States and 3rd largest population in Texas; the city of Houston has the 4th largest population in the United States and largest population in Texas. DFW is the 4th largest metropolitan area in the US, while the Greater Houston area is the 5th largest in the US. There is also contrast between the Rangers and Astros in their ballpark and uniform histories. The Rangers, until 2020, played in open-air stadiums (Arlington Stadium and Rangers Ballpark in Arlington), while the Astros have mostly played in indoor stadiums (Astrodome and Minute Maid Park). While the Rangers have traditionally worn variations of red, white, and blue to represent the Lone Star flag, the Astros have changed color schemes (e.g. Shooting